Nope, i'm not living in america, so i use the normal 7610...
When u see 7610's online and they just state it as "7610", it's most probably the international version, unless they state it clearly as a 7610b, i suggest u don't get it. I think the safest way to get the 7610 is to get it at ur local store... the 7610b has been released in america already right?? I guess if it is, it shouldn't be too hard to find at ur local stores. The last thing u want is to order a 7610b but end up being delivered a 7610.
I think 3230's very similar to the 7610 except for the cam. If u really want that extra 0.3 megapixels than maybe u might wanna consider 6630 and 3230 (which have 1.3 MP cams while 7610 only has 1MP)
I personally think that 3230 and 7610 are not really different in specs other than the cam. Both have mono MP3 playback (which is really bad btw), symbian, rs-mmc, 10 mins video recording etc. I find that 7610 looks better though... but it's up to u...