Right, since this thread is likely going to be a whole bunch of people wanking over how good this game is, let me start off by saying what ISN'T good about it.
Ammo instead of cooling, for two reasons. One, it takes a big shit on what the first game established. This is like when they said that the force is controlled by Midiclorians. So, they have this established system of weaponry that works well and makes sense, and somehow in the last 2 years we lost all record of it and have reverted back a century. What the fuck is up with that?
Second, it takes away all of the challenge. In the first game, if you just jump out and shoot like crazy, you'll overheat in seconds. This pretty much makes you SOL for the next 10 seconds, in which time the enemy rips through your shield and kills you. With ammo, it makes it so that you can just shoot like crazy, reload, and continue to shoot like crazy. And it's not like you have to actually worry, because ammo apparently grows on trees.
Also, it's just like every other game. Apparently they don't feel the need to stand out or do anything differently.
On that note, like I said before this game isn't an RPG anymore. It's a shooter where you talk a lot. I mean, really, there's hardly any difference in each of the weapons, there are maybe 5 or 6 different skill options, compared to the 12-15 that were in the first game, and the upgrade system was completely removed. I mean, really. San Andreas was more of an RPG than this.
Also, there's no challenge anymore. It instead follows your typical shooter style of difficulty, which is "Throw as many enemies at them as possible hoping that they'll get shot, have plenty of insta-kill enemies." Whereas the first game actually forced you to think about what you were doing. You were able to use your biotics ONCE, and then you had to wait a whole minute before you could use it again. This made you actually think about which abilities you were going to use when, instead of just using the same one every five seconds. I actually got bored and quit after a few hours, and that doesn't happen to me often. Also, why is it that my Vanguard is suddenly able to use every gun? I should be able to use pistols and shotguns, nothing else.
Now don't get me wrong, it's a pretty good game. It looks good, and it's kinda fun, but that can only carry it so far before it has to learn to walk. If it was a stand alone game and not a sequel, I'd give it about an A- or B+, but since it's a sequel to a great game that it doesn't live up to, I'd give it a solid B. Above average, but not Bioware's best work.