When thinking about the merits of the mod, there aren't any. You can get mini computer cases for cheap, and they would work much, much better than his trashcan. So what we're left with is the "look a trashcan looks like the Mac Pro" joke with a more literal application, which is, as I said, kind of funny. Though who's to say a trash can isn't well designed?

Edit Since the link switched to the original forum post with more pictures: I must say the project was quite impressive and the end result is cool, though I still stand by my original point.