I should have mentioned that I'm using WOAI for FSX. I have neen considering UT2 for a while now and dithering about whether it's a good investment. What do you think? I do like the queues and general traffic chaos at busy airports, plus WOAI doens't have that great a range of airlines. Does UT2 deal with the FS tendency to stop planes that are a long way behind you or allowing you to crash into other planes? What about parking at correct gates? Does UT2 make use of the AFCAD well?
I've been using UT2 for almost a year now, and I'm very impressed. I wish I had done it sooner. I used to use WOAI, but my airports never really got the "feel" of any form of density. UT2 parks the correct AI at most of the correct gates. It does deal with taxi speed issues a bit, but it's FSX's fault for the poor taxi and AI "awareness" of you. That's something that can't be fixed by an add-on, as FSX controls the ground handling of AI (at least that's the way I understand it). Another great feature is that if you are on final approach, and FSX (as it usually does) clears a couple other planes in front of you, you can hit a hot-key to drop them, so you are clear for landing.
UT2 is handled by simconnect, so traffic is streamed in. It doesn't use BGL files as WOAI does. There are inexpensive schedule updates a couple times a year, but they aren't needed unless you want to have the most up to date schedules.
Overall, it's well worth the cost, because all the airlines are there, and you don't really need to manage anything. One of my favorite addons.