I've heard that most people don't like the recoil on the guns in the game. Not sure if that's his issue with the aiming system, but if it is, then it's a moot point to me. But I can understand some people won't like it, especially after games like COD4 and CS teach people that yes, it is possible to reach out and touch someone across the map with an MP5 on full auto or an AK47 (I still don't understand why this is the most accurate assault rifle in CS).
As for framerate issues, it's only while loading. And there are plenty of graphical issues in Gears of War 1, and that was praised for it's visuals (screen tearing, texture's loading slowly or in the rare instance not loading at all).