I played the beta and loved it. I didn't expect that the story, the cut-scenes, and voice acting would make that big a difference to me, but they did. The story pulls you in, and the acting is generally superb. For the first time in an MMO, I'm usually able to remember *why* I'm gathering stuff or killing particular enemies. Plus, the story arc pulled me along: I wanted to know what would happen next.
Personally, I really enjoyed the combat. You don't just walk about a rat, one at a time, and engage it in one-on-one dueling. Instead, you usually dive into a group of 3 or more enemies, and you battle them all at once. My Sith Warrior really felt powerful even at level 1, slashing away with very nice animations. The game encourages you to group (but rarely requires it) by awarding you "Social points" and "Social levels" that lead to certain rewards. Flashpoints are like dungeons in other MMOs; they require a group, and they're quite fun, but they require an hour and a half or more to complete.
Also, you earn companions -- five in all, eventually -- that are more interesting than "pets" in other MMOs. You can talk to them, and they have their own story lines, plus they do crafting and other missions for you. You can even have romance with them in some circumstances. They also put out significant damage; if I fight without Vette at my side, I take longer to bring things down, and I take more damage myself.
Having your own spaceship is neat. It functions a bit like the ship in "Knights of the Old Republic" or "Mass Effect 2," with crafting aboard, lots of rooms to poke around in, companions to talk to, and of course space combat. Space combat is just a 2D rail-shooter, a diversion more than anything else, but still kinda fun, and certainly Star Wars-y.
There are a few negatives. Character creation is good but nothing special, with a limited number of body types. There are a bunch of minor bugs, none of which really annoyed me, and many of which may be stomped by release. For some people, the core gameplay is too "traditional MMO" for their tastes; the big innovation here is story and voice acting. It feels like "Knights of the Old Republic" in an MMO setting. Me, I love KOTOR, and I think it works great in this genre, but some people want more innovation. I suppose such people should look toward Guild Wars 2 or A Secret World, both of which look interesting.
For me, though, SWTOR promises to be my MMO of choice for a long time.