Here's how things are going around here (I'm currently in the US)

$300 gets you an iPhone 4 provided you sign a 2 year contract with AT&T – the phone is not unlocked for you it stays locked with AT&T and you have to pay a monthly fee for the service,

$600/$700 (depending on 16/32 GB) get you an iPhone 4 no commitment contract – this means you don't need to get two years of service from AT&T – but here's the sad part, the phone is still locked to AT&T and the iPhone Dev Team (the authors of the best unlocking tools on the web) still don't support the iPhone 4 (they unlocked iOS 4 on iPhone 3GS though).

Another thing to keep in mind: the iPhone 4 uses a MicroSIM tray, what Alfa/MTC use are MiniSIM which are bigger. So people claim to have successfully cut it (it's just plastic) and had no problems - others claim that it will affect 3G speeds (something we don't have to worry about in Lebanon).

Finally, I got mixed answers from the Apple Geniuses (the people wearing blue that answer all your questions in an apple store). One genius in the Apple Store in San Francisco told me that I can buy the no commitment iPhone using my Lebanese passport while another genius in Apple Store Los Angeles told me that I need to be an american citizen…

As for some early-adopter bugs, I heard some problems with the signal being grounded when the phone is held in a sweaty left hand (only happens on some batches, not all) this can be fixed using a cover (apple sells those, or just go incase) – other problems include weird behaving flash (LED, not adobe :P) and yellow-tint on screen. Again, those problems are not being reported on all phones and you can a one year international warranty from Apple in case something goes wrong.