On Friday, July 16th, Apple held a press conference to quell concerns about the iPhone 4 antenna problems. In his address (which you can watch in full here), Steve Jobs, CEO of Apple, Inc, discussed some of the problems people have reported and how they want to address them.
Essentially he offered the only two logical solutions: if you want a free bumper case, you can get one...if you are still unsatisfied you can get a full refund on your purchase for 30 days. Note: if you are a new AT&T subscriber, you can get out of your 2 year contract, but if you are a RENEWING subscriber, you may not be able to get out of it (presumably you could get yourself a 3GS, though).
There was a bit of hemming and hawing about how their phone really isn't at fault as much as the entire cell phone industry, but if you want to hear that, check out the whole press conference as linked above.