I think this is the key point... and although I have plenty of confidence in BioWare, I think that they're doomed to fail when it comes to this. Granted, it may not be at level 10, but the MMO model simply doesn't support storytelling of the nature that folks are used to with BioWare's single player RPG's. Granted, I've not played it -- but the amount of time people spend playing MMO's simply dwarfs the gameplay in a story-based game like KoToR -- and MMOs don't make money with content. They make money with subscriptions, and keeping people playing for long stretches of time. I know that they've been working on this game for years... and that the idea is that each class has its own deep, involved storyline. But... they've been working on this game for years, and there's a LOT of money to be made up. At some point they're going to hit the point where players will burn through the content in story content in X months, and I think that (X*subscription rate) is less than the amount they'll need to make it worthwhile for EA -- if the gameplay is story-centric all the way through.
At some point, I think they're going to run out of story and need to keep people playing with the MMO standards of incremental, rare improvements that can take months to achieve. The same model that Everquest, WoW, and pretty much every other longterm MMO has depended on. At the very least, the time between plot points in each character's story will stretch out and the day-to-day play will descend into the "old MMO grind" with rare and hard-earned story progression.
Now granted... I've not played it. But I did spend a lot of time playing EQ back in the day, and I have played (and loved) BioWare's single-player games. I'd like to see this game succeed (even if it turns out to be a fancy WoW clone in the long run), and I've no doubt that it's well made. But I'm just not sure that they can really deliver as much story-driven gameplay as an MMO player can consume.
The good news is, that nuts to bolts, it's an extremely well made MMO in a rich universe where the only complaint is that it's essentially too familiar because of how similar it is to WoW from a systems point of view. From a technical standpoint, I'm amazed at the polish. Everything has worked so far, without a hitch. I haven't lagged out or been disconnected once. Could be that it's because of early game access that I'm not experiencing that, but I've come away impressed.
They do add some interesting tweaks to some things that are nice; quests are very rarely "kill x number of these," they're typically about finding some artifact, some information, or performing an action that advances your story while piling up a body count manifests as a bonus objective yielding extra experience and cash. The visual element of your character is something the player has a lot of control of, most of the best armor items don't have stats on them, but modification slots where one places stat mods. This allows you to conceivably wear a robe you really love at level 15 until you're level 50, just keep upgrading the mods in the slots, which I think is a cool tweak and something that always made sense to me. It may have been in another game, but I've never seen it before and it's refreshing to see here.
I've yet to hit end game, obviously, but like you I wonder how the flashpoint/missions will go once people are running them multiple times daily or if that's even an end game requirement. I can see going through voiced conversations you've had 10 times becoming exceedingly tedious and irritating, unless they just start to cut them out.
As for more personal experiences playing the game, I started out as a Sith Inquisitor/Sorcerer and wasn't really feeling how the class played, it was pretty uninteresting and while the story arc of finding powerful knowledge was fun, I didn't like the skills or how the class was built. Oddly enough, I decided to give the Republic version a whirl, and for some reason it's night and day to me. The Republic brand of Dark Side is far more...selfish and indicative of moral relativism rather than the Sith teenage boy version of mindles cruelty and I didn't think they were able to capture the idea of a behind the scenes super strategist bent on mastering the Force through knowledge. Any kind of confident answer sounds as though he had a massive slave inferiority complex and it got irritating. But I was only level 13. Also, the visual style of the class abilities I find to be far better for the Consular, as PULLING A GIANT ROCK/DROID/DEBRIS FROM THE GROUND and tossing it at some poor fool never gets old and is far more exciting than tiny static discharges you can barely see from the Inquisitor. Again, the skills are numerically identical but I found the overall feel of the class more enjoyable. I may go back and try again, but I think I'd find my Sage hard to pull away from now.