Just upgraded iPhone 3G FW from 3.1.3 to 4.2.1 using Snow Breeze 2.2 as I need to unlock via Ultrasn0w but have found it's very very slow..... is this the norm for 4.x FW. I enabled user wallpaper through Snow Breeze, have I made an error here? It's frustrating to use as my IP4 is so much faster!
If you disable multitasking and wallpaper it should increase performance significantly. Otherwise it will be slow, that's normal on a 3G on 4.x. Like iPittsburgh said though, consider taking it down to 3.1.3 as it's the best in performance for the iPhone 3G.