I sort of like the design of the DW one that came with my 5520-2. My only complain is that the release mechanism is too stiff. I have to club iit hard with the stick (sometimes more than once) to get the top hat to drop. A nice quick tap should do. Unfortunatly its not a user serviceable part.
The new Tama one is by far the best out there at the moment. I have the Pearl ones, and although they work fine, it is hard to hit them sideways to activate, and you can't adjust the amount of play between hats when activated like the new Tama one.