Way back in history, actually, 2 years ago, when I first became interested
in recumbents, I test rode first a LWB with USS and felt so natural, steady
and comfortable, that I figured it was the way to go for me.  Then I test
rode a SWB with ASS, and was promptly convinced beyond a shadow of a doubt
that LWB with USS was the way to go for me.  The SWB/USS felt squirrely and
unstable, and I couldn't track very straight at all.  I ordered a (Lemle)
Lightning Tailwind, the same model as my first test ride, and was more
pleased with my choice every time I rode it.

As it so often happens, my need for speed to accompany my need for comfort
necessitating finding a recumbent that I could ride on faster club rides.
I decided on the ATP Vision SWB with, of course, USS.  It fit the bill quite
nicely, as I was able to ride with the big dogs in just a few weeks.  My
happiness was complete.  Or so I thought.

As time went by and I got the chance to try out other recumbents of all
varieties, I still didn't feel as stable with ASS as with USS, but already
realized I could get used to it.  Indeed I did, with my Doppler CLWB folder
which came standard with ASS bars.  By this time, a year+ after I got my
first recumbent, I'd put on somewhere between 5000 and 7000 miles on my
bikes, and felt certain that I reached nirvana.

My preconceived notions about ASS had been dented a bit by the Doppler.  I
thought my arms would get tired.  They didn't.  I thought my hands would go
numb.  Nope.  I thought it wouldn't be stable.  Wrong-o-rooney.  Hmmm, I
thought, maybe it would get me more aero on the Vision if I had ASS.  The
USS bars are quite wide.  I remembered ASS being a very twitchy ride, but
maybe now that I'm more accustomed to it, it might not be that bad.

I had to opportunity to try it out at the GONJOR ride in October.  Lloyd
Abrams was there with his R-45 with ASS, and he let me take it out for a
spin.  It's amazing how you can gradually get used to something without
even knowing it.  The ASS bars seemed very comfortable and manueverable.
I could make turns in a much narrower space, and had no trouble riding a
straight track.  That was it.  I finally ordered the ASS conversion kit
for my R-44 and had it installed just before the Thanksgiving weekend.
I took it on our club's annual Turkey Trot Tour in beautiful rural White
Springs, FL, about 1/2 hour south the the Georgia border.

When we arrived there Thursday, Jeff and I had only a few minutes to ride
the bikes before dinner.  We took off for a short ride to check the bikes
out, and it felt great, definitely more aero and faster, although Ricky at
ATP thinks it's psychological.  Who cares, as long as the computer says so!

About 3/4 of the way back, I asked Jeff if he wanted to try it.  We switched
bikes about a 1/2 mile away from the campground.  Man!  It is amazing how
different the view is from on top a Merlin road bike.  I felt like I was
going to pitch right over the handlebar any minute!  I suppose you bicyxuals
riding both don't have that problem, but when all you ride is a recumbent,
it's really weird getting on a trad again.

The next day we did a 62 mile ride and I found other reasons to love the
ASS.  It's easier to move the bike about, having bars at just over waist
high instead of having to bend over to hold the USS bars to keep going
straight.  (The USS bars on the Vision seem to want to pull to the left
anyway; the ASS tracks straighter without having to hold them in place.)
My mirror doesn't get messed up if I have to lean the bike against a wall
and it's in a better position for seeing behind.  Being able to make a
tight turn was also a marked improvement.

One thing with the Vision ASS:  several ASS fans have said they didn't like
USS because they don't get any ventilation under their arms.  I found the
exact opposite.  With the Vision USS, I got more armpit air than with the
ASS.  I think the reason is because Vision USS is wide, so my arms weren't
plastered to my sides.  The Vision ASS is rather narrow and close, so my
arms are bent and my hands are only a foot or so from my chest.  It's a
comfortable position, but I found myself lifting my elbows out laterally
to get some cooling breezes now and then.  In any case, it's not worth a
tick in the negative column.

So here it is, the confessions of a convert to ASS.  I can now safely
say that both are great, as long as they are on a recumbent.

The current discussion on USS vs ASS safety gives an opportunity for me to
beat a drum that I have bashed away at before.  
IMHO, it is vital in a crash on any form of HPV without an airbag or cushioning 
enclosure to get one's arms out in front to protect one's head and spine.
Better to break one's arms and collarbone than one's skull or spinal column.
My experience with forward crashes with USS recumbents, SWB & LWB, is
that my arms have always gone forward where they should go, and have
taken the damage.
My experience with regular bikes is that people tend to grip the 
handlebars like crazy, as if they provided any protection.  Horrible
injuries have often resulted.  (These in cases in which I have been an
expert witness).
I've seen no accounts of what people do in an accident on an ASS recumbent.
The danger is undoubtedly far less than when on a standard bike.
I confess that, despite preacher Bill's pronouncements, I am unrepentently
biassed in favor of USS for safety, comfort and, I believe, lower weight.
If one is going to fit a fairing, I acknowledge that ASS provides a great
support.  The contribution of fairings to safety or danger is another 
topic I'd like to see discussed some time.

 David Gordan Wilson writes...
>it is vital in a crash on any form of HPV without an airbag or cushioning 
enclosure to get one's arms out in front to protect one's head and spine.
Better to break one's arms and collarbone than one's skull or spinal column.
My experience with forward crashes with USS recumbents, SWB & LWB, is
that my arms have always gone forward where they should go, and have
taken the damage.
My experience with regular bikes is that people tend to grip the 
handlebars like crazy, as if they provided any protection.  Horrible
injuries have often resulted.  (These in cases in which I have been an
expert witness).
I've seen no accounts of what people do in an accident on an ASS recumbent.
The danger is undoubtedly far less than when on a standard bike.
I confess that, despite preacher Bill's pronouncements, I am unrepentently
biassed in favor of USS for safety, comfort and, I believe, lower weight.
If one is going to fit a fairing, I acknowledge that ASS provides a great
support.  The contribution of fairings to safety or danger is another 
topic I'd like to see discussed some time.<

     I have to disagree with this. How can having your arms at your sides
(probably the worst place for them to be in a crash) be safer than already
having them up & in front of you like on a bike with ASS handlebars? On ASS
your hands are pretty much exactly where you want them if you crash, up in
front of your upper body. On BSS you have to get them up to this same
position, this takes time (& in many crashes thats something you don't have)
& it removes your hands from the bars & any further possibility of
controlling the bike. I'd much rather have them in position already AND still
on the bars so I can move the bike & try to improve my chances. Many times
I've had close calls where I managed to escape a crash in the last second, if
I had BSS & had brought my arms up into a crash position I would have lost
control of the bike. On BSS at some point you can no longer eat your cake &
have it too, you have to decide to steer OR get into a defensive position, on
ASS you do both at the same time.
   There are many ways to crash, some with warning, others occur so fast you
don't have time to react at all, & in every situation I can think of I'd
rather have my hands & arms in front of me & in control of the bike. ASS is
safer in a crash.
     BTW, I've crashed my Stealth a bunch of times riding offroad & as a long
time (14 years) MTB rider I've crashed hundreds of times, & witnessed
hundreds of others.