Does anyone have experience with buying an officially unlocked iPhone 4 in the US?
No, this isn't possible to do through official channels. The officially unlocked phones are unlocked from the manufacturer; this isn't possible to do after the phone has been provisioned (otherwise the iPhone hacking community would be all over this avenue rather than going after security holes in the baseband to achieve the same effect). Because if their agreement with AT&amp;T, Apple does not sell these units in the US, and every distributor outside of the US has to agree not to sell the units to US customers.