I have a level 29 Sith Juggernaut, a level 39 Jedi Guardian (both tanks) and a smattering of other classes either on their home world or the second world of their faction's storyline. My wife and I play together, playing a tank and healer combo, one world at a time, and then flipping to the other faction.
The Old Republic is probably the first MMORPG to emphasize the "RPG" at the expense of the "MMO." Which is to say, if you loved Dragon Age or Mass Effect or KOTOR, you'll love this game, at least the first time through on a faction. (I'm not sure how many times I can play through Coruscant, for instance, no matter how much I want to see all four Republic class stories.)
But as an MMO? Well, there are problems, chief amongst them is that there hasn't been an MMORPG to date with such a striking difference between the leveling experience and the endgame. In EverQuest, City of Heroes, Dark Age of Camelot, World of Warcraft -- indeed, most MMOs -- the leveling experience and endgame have a lot in common.
In WoW, the most popular MMO, you level up with a variety of quests, run through dungeons, engage in PvP and do tradeskills. Starting at level 60 -- long before the current level cap -- you can participate in raids, which are groups between twice through eight times the size of a regular five-man dungeon group, to take on extra-tough challenges. But for many players, they continue playing at level 85 much as they did at level 20 or 70 or whatever. They log on, they do a quest or three, they fight the enemy in PvP, they do some tradeskills, they log off.
SWTOR, though, is dominated by the class storyline, with "group quests" available to pad things out. And these ... stop. If you're not already playing SWTOR, that may not sound like a big deal, but it really is. I've got a lot of friends who are hardcore, even fanatical MMO players (I'm actually in two separate guilds on the Republic and Empire sides, letting me see even more of the responses of MMO vets), and they're bailing out, because not only is there little content once the class story line ends, the prospect of rerolling and doing Coruscant or Tattooine a third or fourth or fifth time (and bear in mind that most worlds are used by both factions) sent them screaming for the door.
I think this problem will eventually be fixed, but it remains to be seen if it'll be in a free patch, DLC (I would buy new companions for $5 in a heartbeat) or an expansion, and how many of each it'll take.
The game is fantastic the first time through on each faction. I can't wait for my Sith thug to become first a Sith Lord and then a Darth -- the Sith sometimes border on unintentional Dr. Evil parody, but they're a lot of fun, despite that. And while my Jedi Guardian doesn't have nearly the same amount of personality -- if you want your Jedi to be a good guy, about the only dimension he can have is whether or not to make out with his padawan -- the story is incredibly epic.
My prediction is that this will be the #2 MMO for a very long time, but that it'll never really challenge WoW which, even in its current moribund state, still has 10 times (!) the subscribers.
Bioware makes great RPGs, but their MMO design shows a lot of laziness:
* Under the hood, SWTOR is almost exactly WotLK-era WoW, down to using almost all of the same hotkeys and not using many of the improvements Blizzard made in the next expansion or has announced for their new one coming this summer. (I never knew how glad I was to not have to buy incremental upgrades to abilities any more until SWTOR forced me to do it again.)
* The interface is atrocious. (The auction house is borderline unusable, for instance, with some portions of the interface not working, seemingly at random.)
* Sometimes you can see another character's story cut scenes, sometimes you can't, even when there's no logical reason to lock them out. And attempting to travel around the galaxy on a friend's ship (which the devs explicitly say is possible) boots your character out, leaving you in the starport.
* The camera leaps around during responses in quest dialogues, with sometimes half a dozen jump cuts in 60 seconds (and not intentionally -- sometimes the camera is just moving up or down slightly), showing that no one on the team either took the feedback during the beta seriously or that they're massively backlogged catching up even now.
* And customer service? I've had a ticket open and unanswered since the first week of the game. (And the ticket is uneditable, despite the interface claiming it's possible to go in and tweak existing tickets.)
My wife played through Dragon Age: Origins eight times and the Mass Effect games more times than that, and even she's already leery about playing through SWTOR eight times to see all eight story lines. I know I'd happily pay $20 for a world pack to give alternatives to the non-exclusive worlds, just so that I won't find myself running around the same places again and again. (I understand why it's designed this way, and would happily subsidize an art team building new assets for alternatives.)
My expectation is that we'll get at least one character per faction to the cap and deactivate until the first expansion or until there's a new chapter available (at least) for each class.
The game offers a great, authentic, fun experience, especially for Star Wars fans (SWTOR made me realize how this really isn't my favorite sci-fi franchise, but I don't think we'll ever see a Hitchhikers Guide to the Galaxy MMO), but the team needs to improve the MMO part of the experience to make it match up to the amazing quality of the RPG portion of the game.