One thing I remember from os5 beta days was that they got a lot faster and smoother as the betas went on.
I think you might want to refresh your memory.
The iOS5 betas were all over the place.
One update was an improvement for iPhone 4 uers but a mess for 3GS users.
The next would be the reverse.
One beta improved battery life, and the next was a nightmare.
One beta would fix some apps and would break others.
Just go back and read all the threads.
A steady consistent improvement it was not.
I'd be interested in the performance it gets.
Thanks!
I updated my now old and unused 3GS to iOS 6 beta 1 just now.
I am actually finding it a bit smoother and zippier than iOS 5. I did an "update" in iTunes to iOS 6 so all my apps and settings are there. It doesn't stutter or hang as much.
While I may be on Airplane Mode without a SIM, I can say that the standby battery times have improved greatly, and usage time is improved as well. I can't attest to that with an active phone service on a 3GS though. I'd imagine there'd still be a bit of an improvement.