Great game (no spoilers)
This is all you really need to know.
If you like first (or third really) person shooters, like a nice tale, awesome character development and a reasonably addictive game that will keep you buy for at least 30-40 hours, then this is a good game to get.
A lot of good work was put in to this game and it shows from the beginning. The story may go up and down and you may encounter parts you don't particularly like.. but it doesn't change the fact it was a pleasure to play.
Anyone who likes gaming, shooting and a brilliant story, should (like all the others) buy this mass effect.
Just gonna do a quick pros cons in case you wanted some more info
Pros
A reasonable length
Some incentive to reply
Great characters
Fun combat
Customisation is enjoyable
Story is engaging
Cons
If you don't have a ME2 save handy, there are some things you'll simply miss out on. (this is pretty much just relationships that wont develop unless they were present in me2)
Character creation could be improved
Some of the search and scan missions can slow down the pace a bit
Some work to be done to the end of the game...
But over all. You'll have a blast playing this. It's a very well done game.