TSX:
-Sunroof thing like 2hondas mentioned.
-It doesn't play MP3 CDs.

-AUX input angle is absurdly annoying to get to. Its under a cover for some reason too.
-The battery rundown protection doesn't seem to apply to the interior map lights.

BMW:
-Really irritating beeper.
-There's no light to tell you cruise control is on.
-No way to activate manual mode without actually shifting. What if I want manual mode without changing gears?
Merc:
-iPod + AUX interface is in the glove box.
-Amount of glove box space when open is vastly more than amount of space when closed. So its hard to tell if stuff will actually fit when you close it.
-No way to "hurry" the voice prompt and just enter the next command. You have to wait for the stupid thing to finish talking.
-Absolutely refuses to transfer my cell phone contacts.
-Only the left side mirror auto dims. Not that I like auto dimming exterior mirrors, but what the heck?
-The mirrors heat up
really slowly and don't get hot enough to really get rid of rain (the TSX and BMW get plenty warm and quickly to boot)