Some of them are
* Keyboard feeling like sandpaper
* Broken power brick, excessive force needed to connect or disconnect the power cord to the brick
* Battery issues such as loosing power to quickly or fluctuating in reporting number of load cycles
* Sound problems, crackling or dropped sound for a few seconds.
* Wireless issues such as kernel panics
* Assembly line issues, such as abused laptop shipping where the mouse or case is dented.
* Current going throught the case, in some cases its very high specially near the ethernet port if you use shielded ethernet connector and touch it and the case with the same hand. I have no idea as to why.
But I doubt these are common except maybe for battery issue, and these are I had myself, but Apple compensated me and treated me well and I like Mac OS X so im staying. But im not satisfied with their QC and I wish all of this didnt happen, least not after the third replacement where I was satisfactory compensated.
