A lot of the T2K discussion revolved around the flaws in GDW's assumptions about a post-apocalyptic America, which I'm not going to go into here (there's a brief synopsis of the now-alternate history in the Wikipedia article) except to say that the authors saw America dissolving into anarchy as a result of the three-cornered civil war between the civilian and military governments on the one hand and New America on the other, aggravated by a TTAPS-inspired "nuclear winter" drought. Now, I've always assumed that if you ran a T2K campaign based on the original version's modules* with a fairly competent group of players, those players would successfully complete the modules or at least collect enough information and do enough damage to allow whichever faction they're supporting to come out on top. Players (and NPCs) will also find a way to get around the holes in the original scenario so that things don't fall completely apart, because there's no benefit to the characters -in the long term- living in a country where everything is slowly but inexorably moving toward complete entropy.
We also talked at length about the problems inherent in Traveller, specifically those associated with getting and keeping a suitable jump-2 ship with which to have adventures. It's been argued on the Traveller mailing list that the dice are loaded and it's virtually impossible for players to make a go of things without resorting to crime on an epic scale, but I would say rather that the problem lies in the fact that Traveller requires an ungodly quantity of work from a GM just to set up one sector of worlds in which his players can adventure. Also, in the "mainline" Third Imperium, it's damn hard to find a space in which a tramp freighter can compete with the megacorporations. I'm not saying (and neither is therevdrnye) that it's impossible to have a good time in this system; the character generation system can be a blast all on its own. It's just that unlike D&D, you can't just roll up a bunch of characters and go looking for trouble. Civilization, in the form of the most ungentle Third Imperium, will get in your way and make you stop causing trouble, usually in a painful and final way. And there you are.
Still, I have to say I'm really tempted to get a T2K campaign going sometime, because even with the standard modules there's some curveballs to be thrown at players to keep them on their toes. :)
*Listed on page 5.