Why I like the changes:

They absolutely did ax the bad, and improve the good. Mass effect's strength was always in its story, its characters, it's world (in an abstract sense. I know you can't really explore a lot in either game), and so on. All of those things were refined and improved. Mass Effect 1 over-reached, while its sequel knew what it had to do, and executed every part very well.

What I didn't like:

I love RPGs, I really do. I don't mind playing other genres at all, though, so I didn't miss most of Mass Effect 1's rpg qualities. Some things I did miss, though, were the following.

1) The Citadel. (Yes, I know it's not really an rpg element, but I'm starting with this.) I actually thought a lot of the other areas were more "alive" and fleshed out than the random areas in the first game, but the citadel of the second was very lacking. I won't give details for fear of impinging on the no spoilers rule, but suffice to say that nothing of the old is in the new. It's not even the biggest populated place anymore. I mean in theory it is, but the place you go to is not. I missed it.

2) RPG element time: finding gear. It's true that gear wasn't very situational in the first game. You never really had to swap, you just found upgrades. Still, it was exciting to find upgrades. In 2, you find basically two weapon upgrades the whole game, and a couple of meaningless, inconsequential armor "upgrades." I miss the "stuff."

3) Skills. Seemed like in the first game, you had a bunch to start with, then got a bunch more as things go on. In ME2, every character starts with a few (4ish), aaaaaaaaand. . .that's it. The problem is partly alleviated for your main character by importing a high level ME1 character (gets you an extra skill to start off with) and a certain thing you can research during the game, but still. I was expecting a lot of neat new things you could do, and instead there were a lot less, and they were far less powerful.

4) Leveling up. This is a beef I have with most western rpgs, actually. To ensure good pacing and standardize boss fight difficulty, they severely limit the amount of leveling up you can do. Mass effect 1 was guilty of this, but it was still possible to be a level or two higher than normal by making sure to kill every enemy in each area. Mass Effect 2 removes this. You get experience for completing missions, and that's it. You'll almost always gain a level after every big mission, and almost never otherwise. Big missions give you 1-2k experience, medium sidequests give you 125, and small ones give you 40. Period. It takes an average of a thousand experience or so to level up. Meaning that if you do every sidequest in the game, you'll end up MAYBE one level ahead at certain parts of the game. Not all of them, though, because if you bump up a bit, the big-mission xp may not give you the bump all the time, or whatever. Hard to explain, but you get the idea. Frustrating. The only reason to complete sidequests, really, was to find new upgrades.