There are two main elements of gameplay that were altered because of community feedback. The first being aim-assist for controllers, the other is apparently nanovision.

There will always be people who complain over any element of design, while Crytek as the designer needs to assess what is being said from a logical standpoint first before simply changing things. This is doubly important this early on as the experience of in-house testing far outstrips the experience that can be brought back by the community.

Don't simply alter gameplay mechanics on a whim. This game is complex and strategies for use of gameplay elements have not had time to cement themselves yet. A good example of balancing of gameplay mechanics is Blizzard's patching of Starcraft2. This may not be reflected in the opinions of the masses, but from commentary provided by the top tier of players (note: not from the official Blizzard forums!).

When you do alter something, the same approach applies, you must wait for the players to learn to use the alteration. Leave nanovision where it is for now and see how it is used, listen for players' opinions on the matter but don't just agree with them straight out.

Alternatively, private servers with the ability to alter the game setting will let you see what good changes are simply by the volume of players and removes your responsibility for balancing the game at all.

What was altered about aim assist for controllers? Personally i wish it didn't exist at all. It's got the Black Ops magnetic, lock-on effect which is so annoying.