Well I did notice that when I used the bluetooth keyboard and magic mouse with my mac mini that actual performance would drop noticeably, with TONS of beach balls. Now that I have switched to a wireless MS keyboard, and logitech mouse, the machine actually works like I would expect it too! Go figure. Apple is putting WAY too much effort into iGadgetry, and not shoring up the quality of their other products. Stuff shouldn't be breaking the way they are right now (Mac Pros, iMacs, laptop issues with hard drives, blue tooth devices...practically the entire line!).
At this point it seems like you either have to live with the problems or move on to something else.