I have noticed a drop in performance after upgrading to v4.2.1 of iOS. Especially noticeable when opening grouped applications. I wonder if it is possible to downgrade..? This is a big downside for me – if I knew about this, I would not have upgraded. Period!

Too late for that now. I have a non jailbroken iphone, so I’ll have to stick with this version I guess. One of the pros, is that the “Find my iphone” functionality is free with this version. And it works!