ive already posted this as reply in another thread, but i figured i would share with everyone else too. feel free to contribute any other tips u may have regarding iOS 5 optimization!!!!! ive been playing around with iOS 5 on my 3GS for a few days and thru trying stuff that ive found on forums and just general trial and error, ive found out some useful info to help after installing iOS 5 or any future updates on ur iDevice. from what ive found, the most fool proof way to install iOS 5(or any iOS) and have ur phone or whatever running its absolute best is doing fresh restore and setting it up as a new device rather than restoring from back up. but then u lose all ur stuff(pics, contacts, etc) which kinda sucks!!! however ive discovered a few things to do after u do a fresh install/restore and restore from backup that will have ur device still running beautifully. the MOST important thing u need to do after the installation from backup/sync/etc process is done is go to SETTINGS>GENERAL>RESET and hit RESET ALL SETTINGS. this doesnt delete any of your data such as photos or apps, it just resets things like your home and lock screen background, notification tones, location services, and ur screen brightness; all things that are easy to change back once ur phone reboots. it will still leave all of the really pain in the ass settings alone(contacts, contact specific personalized ring tones and/or photos, browser bookmarked pages, etc). from what i gather(purely theory here, not fact), doing this resets and deletes all of the invisible leftover fragments of temporary info from previous backup/restores from previous iOS settings that are the wrong parameter/calibration for ur current iOS, which left lingering are serving to affect ur current installations performance and battery life. once deleted, ur phone will run noticeably better. for instance, ive noticed that after installing iOS 4.3.3(i think) that my 3GS home button has been lagging. when i hit it at the lock screen or to close an app, the response is noticeably delayed. with the install of iOS 5 it improved slightly but not entirely. however after doing RESET ALL SETTINGS, the home button lag is gone!!!! not only that but the overall performance of iOS 5, which was already quicker than 4.3 on my phone, is even snappier now!!! battery seems slightly better too, now its about the same as it was with iOS 4.3. another thing to try is go to SETTINGS>MAIL, CONTACTS, CALENDERS, turn off PUSH, delete ur email accounts and reboot ur phone. once u reboot u can enter in all of ur email info again and turn PUSH back on. im not sure how much this helps but ive read it does ur battery some good by getting rid of lingering temporary setting info as well. a few other things that will help improve performance a little: -SETTINGS>GENERAL>SPOTLIGHT SEARCH and uncheck everything. -SETTINGS>GENERAL>BLUETOOTH and switch it off -SETTINGS>GENERAL>RESTRICTIONS>ENABLE RESTICTIONS and turn PING off(leave RESTRICTIONS enabled after doing so) -SETTINGS>GENERAL>ABOUT>DIAGNOSTICS & USAGE and select DONT SEND hope this helped!!!!