I was JB'd on my iPhone 3G running 2.1. I found it a little laggy also but assumed it was because of stinky Winterboard. Once I updated to 2.2, for some reason I didn't try to JB until a few days ago. I am now having all sort of problems and it has failed 3 times (Pwnage Tool 2.2.1, QuickPwn 2.2) on 2 different computers (two macs running 10.5.6). I have nearly given up but have a few more options. I am trying WinPwn on a PC and I am trying QuickPwn and Pwnage Tool on a Mac running 10.4. I am trying that because of the 10.5.6 DFU mode problem. I have a thread in iPhone hacks called "Can't jailbreak 2.2 iPhone 3G!" or something like that. Sorry to get off topic though.
David