Verizon & Sprint have officially released GB domestically. AT&T and T-Mobile have not. I personally have the AT&T version and would like to see an official release, if for no reason other than to help resale value a bit.
Otherwise, I've tried the generic GSM Tab Gingerbread and I currently have Overcome 4.0 on there and it's running quite well. There is supposedly a new official Samsung 2.3.5 firmware out there that's even smoother.