I'll repeat myself here from the original post that inspired this thread, as well as add some clarification based on this poll itself:
I game T20 monthly with a group of five players in a tabletop FTF game. I've been doing so for three years now. The first year was in an ATU, but the last two years have taken place in the OTU and uses 1248 playtest data and fanzine material for support.
I've played T20 since Nov 2002 online as part of an eight-PC PBEM group with Referee, and it has been quite active. This game has been set in and about the Linkworlds Cluster in Ley Sector during 993 and early 994.
I've played CT since January 2004 online as part of a six-PC(?) PBEM group with Referee, and it has been active, but not as active as the T20 PBEM. That game is based in the mid to late 1100s in the Spinward Marches sector, Regina subsector.
I've run Traveller games at numerous conventions and local game days over the last four years, and attendance is usually very high. In fact, I ran the only Traveller games listed in Gen Con Indy 2005's schedule. My Con games are run in the OTU, usually Glimmerdrift Reaches in 993, although a few were set in the Solomani Rim in 1115.
Before I started running T20, I played in a year-long GT game in 2000-2001. That campaign was set during the TNE era, located in a sector coreward of the Gateway Domain.
I'm actively playing Traveller and using the OTU, and I know of about eight other people locally who are doing so, as well. (There's another group of CT Travellers that meet on Monday nights near here.)
I will admit, though, that my next Traveller campaign has a 50/50 chance of being set in an ATU, just for a change of pace. (Otherwise, it'll run in the Hinterworlds sector, which we'll start detailing in Stellar Reaches #5.)
Hope that helps,
Flynn