Sorry I'm late to the party, but I really don't have much to report.
I've had exactly zero problems with Cogs, and have been enjoying it.
I freely admit that puzzle games aren't really my thing, which is why I really liked how the difficulty ramped up slowly, rather than just dropping the user into the deep end, so to speak.
I also like how the puzzles and environments were varied - bells, wheels, steam, fuel, jack-in-the-boxes - keeps it from getting boring.
The main menu music was also nice.
The only things I saw were the jack-in-the-box head was a placeholder (but this is known as I understand it) and the framerate on my system a bit choppy until I turned off the VSync.
Intel Core 2 Dual E6750
Gigabyte mainboard (model escapes me at the moment)
Windows XP SP3