I like the idea of many of these games, but I can't wrap my head around having to keep paying to play. I'm stuck with the mindset of buying a game, and then being able to play it whenever I want, no monthly fee.
Another problem (in my head, at least) is that I'm just a casual gamer. I might play for a week, then take a few weeks off, or just pop in for a bit now and again. Not only does that not work into the pay scructure, it also means that I'm at a severe disadvantage compared to the typical 'nerd in the basement' that is playing these things 16+ hours a day. Being a Level 5 and running around with a bunch of level 142s doesn't really appeal. Nor being a random guy running into teams and clans, etc.
Perhaps it's segregated better than that, but have never really tried any of these to be able to tell. I usually just stick with the single-player games, or if doing the 'instant battle' sorts of situation, just myself versus the computer (or several AI players).
I loved the KOTOR games, and it would interest me to check out the online thing, but afraid of the things already mentioned (plus pissed it isn't KOTOR 3!). If there's a free demo of the upcoming Star Trek one, might give that a try, but can't see paying to stick with it long...