Yeah, put me down for some discoloration and scratches too.
The top part of the mouse (where i typically scroll) has begun turning a light tan color. It also has a few scratches, but i think im to blame for that.
I travel alot, and need to have my mbp constantly on the move, as well as the magic mouse. So i figured the transparent box it came with would make adequate transport for it. Not a good idea.
Inside the box the mouse has a little wiggle room, and since the compartment in my bag i use to move it around fits it in a vertical position, now the mouse presents wearing on the topmost part where it made contact with the plastic top. So i started packing my screen wipe (the black one with the apple logo that came with the mbp) over the mouse to keep it from getting more scratched... but now its discoloring (well, technically its not DIScoloring since its white, i guess u would say its coloring). I cant help thinking the screen wipe is to blame. It just seems too delicate to just have in my bag without a carry case. Any input on this? Does anyone just throw their magic mouse into their laptop bag and have it in perfect working order?