I decided to buy some of those Mr. Clean Magic Erasers to see if they could do anything about the nice layer of dirt that embeds itself on Mac cases over time. They do a very, very good job at removing the grime and crap from cases (used it on two StyleWriters and three Macs) brought all of them back to a nice gray - for the most part. It doesn't seem to correct the yellowing that happens to Macs after like 10 years. But it still does a good job of making them look pretty. I got a pack of 4 for about 9$ Canadian, but I don't know how long each one will last, I mean, this one looks totally dead after just a few machines. I don't like the idea of paying like, $50 to get all my 50 Macs cleaned (plus their keyboards, mice and monitors.) It says don't do it on anything super smooth or glossy, such as the plastics on newer Macs. I didn't test it, but I don't want to find out. Has any one else tried them on their Macs?