Coming from first-hand experience and with some skepticism going in.. I have to say that ToR is a bit unique and far from the typical MMO experience.
In all honesty, there's very little "MMO" involved.. a few flashpoints and areas, but nothing that's game/story dependent. It's probably one of the largest and longest single-player Star Wars games I've ever played (and it's a blast!)
Sure there's a subscription price.. but even if you just paid for one month or 6, you would get your money's worth.
With 8 classes, 3 tiers (or random) skillset trees PER CLASS.. there's (near) endless re-playability. Even the class stories differ... so it's not like firing up KotOR and playing the same story just with a different playstyle.
If anyone has any questions about ToR as far as SP/MMO elements or the game in general, pop a question in the links that Lynk
posted. I'd bet half of the naysayers would be pleasantly surprised if you gave it a chance.. (I did).