Sorry for the rather long post, I start of writing and I just kept going. If I really got into it, id probably write a giant essay ^^
How is it compared to WoW or other mmorpg? I'm only about level 15 at the moment but just not sure about longevity of the game. What is there for a more casual player to do at 50? (Raided 3-4 times a week for too long back in WoW).
What can I say without being a Fanboy....
How it Plays
It is very similar to WoW in terms of end-game and the way the whole game plays. That said WoW is similar to Everquest and MMOs before it. If you looking for something different then the traditional MMO with gear progression, similar PvE encounters and the PvP then you won't get that in TOR.
The Game
TOR has its pluses, the large environments are great, many good communities (such as Kajidic, Pax Republica, Wraith and many more), the main class story and voice acting are amazing and can keep you in the game for few months until you do all the class stories for 8 classes (8 char slots per realm). The voice acting is amazing although can be little tiring once you heard it once, the second time it will get kind of boring, or at least it did for me.
Missing things
There are features that are missing such as UI features as well as Auction House features but these are tiny little things. The PvE content is great, fairly easy and fun but once you do it for the 10th time, it will get boring.
Journey to 50
You level to 50 doing quests or PvP which can keep you bussy and by the time you get to level 40 you should have a good feel of how the game plays and see if you really want to carry on. When you get to 50 there are Datacrons and Achievements (CODEX) to collect (Datacorns, mini stat buffs) and other features. You have the Space mini game which is nice but it gets repetitive quite fast, at least for me.
PvP
Now current state of World PvP is meh, needs to be sorted but its not awful either, its decent (id rate it 5.5/10). The Warzones are great, love them but there is something missing on the competitive side like Ranked Ladders. I am a fan of Arenas although I like all types of PvP, so for me Arenas would be nice if they would make it into TOR (many players oppose this though due to balance issue and other shenanigans). If they want to keep the PvP crown around and interested in the game, they need to work hard on the PvP side of things.
PVE
Already said about PvE but its pretty much like WoWs with tad more lore and meaning to it. I think the current PvP would compare to something like Ulduar. The raids are nice, the normal mode is failry easy, hard is doable but needs focus of course and the Nightmare mode is difficult although with good bunch of people you can do it, its not as hard like fights such as Algalon 25, LK 25 HC and alike ...
Companions and Crafting
Companions are nice as well, really help out with Solo End-Game as you can have a heal, tank and dps companions (each class gets max of 5 companions). You can send companions out on missions and depending on the difficulty, the harder ones take longer to complete. At 50 you can send out total of 4 out of 5 companions for your missions (so you can send companion to do scavenging, slicing or bioanalysis etc.. missions or make them craft items for you).
Crafting is nice, way better then WoWs in my opinion and can keep you bussy at end game doing bits and bobs.
Another thing you can do to is to max companion affection, PvP Valor rank, social ranks and so forth to more out of the game.
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Conclusion
All in All if you like cut-scenes/story, scifi (Star Wars) and traditional MMO styled game like WoW is, then you will like this game.
If you want new kind of combat system, more innovation in PvE encounters and PvP and so. If you don't like cut scenes or story, or might dislike Star Wars then this game MIGHT not be for you.
There are bugs like any other game release has and I am sure they are working on it. If you get to 50 and don't like the game, give it some time so that BW fixes things and gets more content out. They have stated they have 1 year worth of content ready or nearly ready for TOR so that is great.
Patch 1.1 or 1.2 has new things coming up which all really interesting.
http://www.swtor.com/media/trailers/coming-star-wars-old-republic
Patchnotes
http://www.swtor.com/patchnotes
PS:
Hope it all make sense, at least you should get a general idea. If you need any questions answered fire away, il try my best answering them. There are many reviews (player reviews) on MMO-Champion, Youtube and Official forums that you can look for. Don't give in to the hate, the forums is crawled with trolls.
Streaming is done by a guild member, since my PC would .... explode 
