I jailbroke my i4 last night and its running great, no problems at all and everything works.
Here are some apps you may wanna try out:
openssh (allows you to hack in your phone)
iblacklist ( can block out any number from your contacts)
Sb settings ( a good toggle feature )...
I thought about taking mine back and grabbing a Droid X but this phone does everything so well (beside the antenna woes) that it is gonna be hard to part with.
They are in denial.
I picked mine up on launch day and it loses signal when held as noted, I enjoy the phone but I should not have to use a case to get decent reception, manufacturers need to stop using the public as beta testers.
I like my iPhone 4 but I don't like how Apple allowed this defect to get into the market, I'm quite sure they knew about it before the release.
And now you want me to buy your $30 bumper.