I jailbroke my phone about 2 years ago when the firmware was 1.1.0 and didn't have any issues with it for about 6 months then the phone just said hey I'm done and locked up. Now I have a 3G 3.0 and I'm debating on jailbreaking it. Is there like a page that has the number of people that have had issues vs. the number of people that have had no problems? I know that this is my decision but I would at least like to feel more comfortable knowing that my apple warranty will run out before my phone becomes an expensive paper weight, or if my phone will ever become a paper weight.
If you ever experience any problems all you do is reboot your phone or do a restore. There's really no bad effects from jailbreaking except you can take advantage of your phone more. Even though Apple says jailbreaking is illegal I've read a bunch of stories online that if you ***** enough to a "genius" it doesn't matter. So go ahead and jailbreak 3.0, what have you got to lose?