My jailbroken 3G can already mult-task and create folders. Has notifications on the lockscreen, completely customizable. I'd be downgrading if I upgraded to 4.0 to be honest. I want to see what new hardware features the new iphone has before I decide I'd want to upgrade (and have to jailbreak again) or say hello to EVO.
Not everyone want to jailbreak... It voids warranty. I know it's pretty cool and will probs do it when I run out of warranty but you can't really compare them