Zounds!
I had two problems with iOS 5 on my 3GS. One the slowness and sluggishness with its many incarnations and the other that every time I tried to sync contacts from the cloud my phone basically ground to a near halt as it spent hours and hours trying to download my address book and ultimately failed.
I just applied the iOS 5.1 update and it appears to be faster, but even more important to me, I see in the log files that they did some kind of clean-up of data on my phone and then it was able to sync contacts with the cloud. I now have all my data back and am very, very happy.
Apple missed an opportunity to manage all our unhappiness, limit the public complaining and Apple bashing, and save a few customers if they had just communicated with us a bit along the way. I know from the keynote they've sold something like 315 milliion devices and the relative few, by percentage, of us having problems may not seem like a loud complaint, but it still seems a missed opportunity to service their image.
Anyway, after all this struggle and frustration, it looks to be working quite well. Opened a bunch of apps and I'm not seeing any slowdown either.
BTW, all you arrogant numbskulls who got on this board and sounded off about "old" 3GS that we shouldn't expect to work should take note that a fix in the software appears to have fixed the problem. You are all now cordially invited to sit down and shut up. But, of course, I say that in the friendliest way possible. 🙂
greg