Absolutely no aim assist/auto-aim should be present in this game. This game is set up perfectly to be a competitive shooter based on skill rather than cheap tactics (e.g. no sniper rifles or other instant kill weapons, discouraging camping, etc), but the inclusion of aim assist would defeat the purpose of this game.
After seeing devs mention COD-like aim assist and confirming it myself with videos where the target was tracked automatically for several feet, I have no doubt this game will fail to become as competitive/skillful as a great game like MAG. It will likely develop a larger playerbase at first due to it being multi-platform + the fact that it will probably be less confusing (which is where MAG lost many players, MAG has a terrible, terrible tutorial that doesn't come even remotely close to properly explaining how to play the game and left many players with no idea what they were doing), but in terms of skill required and competitiveness MAG wins hands down. MAG has no aim assist, strafing, and low bullet damage that gives players a chance to react and really tests your skills at shooters. Though Brink will seem to have the latter 2 of the 3, the aim assist will defeat the purpose of these features and turn the game into another skilless twitch shooter. Skillfull/competitive gameplay = replayability for many players, and without this this game will suffer a quick death.
Casuals probably don't understand, but something as little as some aim assist can really have a large adverse effect on this game.
You probably see comparisons to MAG a lot on these forums. Take it as a compliment. MAG is a great game, probably the most skillfull and fast-paced console shooter out in the market at the moment, but at release was plagued with many, bugs, balancing issues, and a useless tutorial that teaches you nothing about the game, all of which significantly effected the initial review scores and were not fixed until much later (though the tutorial is still terrible). If you own a PS3 you should check it out. If Brink looks good to you you're going to love MAG (if you can get past getting your ass handed to you by higher level players until you can afford better skills and weapons for the first 10 hours, and the initial confusion of what you're supposed to be doing due to the bad tutorial).
I'm sure Brink will not be absent of those types of problems though...