I'm on a jailbroken ios4 at the moment. I was told to just upgrade to ios5 as it's no bigger of a resource hog than ios4 and has way better UI. Trouble is though that I'm not sure if I can jailbreak. I used a lot of jailbroken apps, the main ones being sbsettings and mywi.. sbsettings is pretty much crucial for running 3gs on a 4+ ios in order to truncunate the cache. Also mywi saves me a lot of money on rip off wifi cards for my laptop.