I originally bought Mass Effect 2 and realised how epic is was. I then found the need to buy the 1st instalment and was hanging out for the 3rd for a year or so until it was finished. Unfortunately I encountered a flaw when I did buy it. There is one problem which the devs seem to have created themselves (on purpose) rather than overlooked, and that is cross platform save/load functions. This version is PS3 and my other 2 are PC. I actually made a mistake while ordering but thought I should be able to load my ME2 character anyway through the Bioware/PSN link. To my dismay this is not the case, and in fact is blocked to a point.
The best part about Mass Effect is that you can start a character in ME1 then play that same character in ME2 and ME3, with your decisions being carried over into the next game. Not having this pivotal part of the game really destroyed my enjoyment but I have ordered the PC version now so I can actually see the flow on effect of my previous actions. I'd STRONGLY recommend getting 1&2 BEFORE playing this as the outcome seems very limited!
As a stand alone game, it's alright but not great. The story was a bit weird, leaving an ongoing battle at the start of the game only to return and have things turned on their head at the end was the biggest downside. Combat, graphics etc are all improved further from the previous 2 games though which is a bonus. The other 2 storylines were epic, this one was good until the end. To be fair, I was swearing at the TV when I got to the very end. A real let down for me, but it wasn't that bad compared to other games.