Well, I have just finished up for the weekend and wanted to write up my impressions. I am a long time WoW player and a main tank for a 5/7 heroic progression guild. I leveled a Jedi Knight up to level 15. I Spec'd as a tank once I was able to choose my advanced class and start picking talents. I did 1 flashpoint (4 man dungeon) and a couple of heroic quests (mini-dungeons that take 2 - 4 people). I also did 3 rounds of PVP, but ended up in the same war zone each time. I figured I would do more flashpoints and PVP, but the story was compelling enough to keep me leveling.
Overall Feel: The game feels remarkably smooth (especially for a beta). The combat is very fluid and as I started to get more abilities I was using 5 or 6 different abilities on each fight. I ran into remarkably few bugs, and even if they shipped today it would be better shape than other MMOs have been at launch. The UI needs a bit of work as it can be tough to figure out what everything does. It is not nearly customizable enough and I really missed threat indicators when I was trying to tank. Hopefully mods come shortly after lunch. Overall though it feels very similar to WoW, especially late TBC WoW.
Leveling: This is where TOR blows away WoW. I did not even care about any of the Republic stories going into the beta, but I really got into the JK story. Having all of the voice acting makes questing and leveling so much more compelling than just reading the quests and clicking accept. Also having light side and dark side choices makes you feel like you have some ownership of your character and the story around you. If you like Mass Effect for its story, you will like The Old Republic. You could play this as a solo game from beginning to end and it would be worth the money... and there are 8 separate stories. I could absolutely see myself leveling every class to max level on both Empire and Republic.
Flashpoints and Heroic Quests: The flashpoint I did was really fun for a low level dungeon. However, I was supposed to be tanking and at level 10 they had not given me a taunt or a threat presence (I got threat presence at 14, I think a taunt comes at 16). Having the story and being able to make choices in the Flashpoints really makes them compelling in a way that WoW never was (since I never really went to outside sources to get the lore in Wow), but WoW is much better about the order it gives you your skills post 3.0. In my opinion as soon as you pick your Advanced Class as a tank, you should get a +threat stance and a taunt. The final Heroic Quest I did was genuinely hard, requiring CCs and line of sighting on certain pulls. My group of 4 was not able to finish the quest as it was either overtuned on beta, or our healer was terrible. I am not sure how much healers should be able to handle at level 14. So I liked the group content, but I did not love it at least at levels 10 - 15.
PVP: Feels exactly like low level WoW PVP so far to me. I liked what little of it I did.
This is easily the best non WoW MMO that I have tried. If the raid content is there, I will most likely be switching. The idea of leveling 85 - 90 (or 1 - 90 on a Monk) without voice acting and a compelling story just sounds painful after getting some time with The Old Republic. Hopefully the endgame is as impressive as levels 1 - 15 were.