We had some. Can't recommend them enough if you're a small family. They're also more flexible -- in a normal dishwasher you'd only put pots in the bottom rack, meaning if you've got a load of plates on you'd have to wait. Not so when either draw can be configured for anything and put on separately.

Then we moved house, and the new one had an old regular dishwasher that often doesn't quite clean bowls properly -- can't quite bring myself to chuck out a working dishwasher to get dishdrawers, but if the dishwasher breaks any time soon...

I had the Fisher Paykel double dishdrawer and found that it works great. We loaded dirty in one drawer and took clean from the other. We always had to put a few clean items away when swapping drawers, but that's a quicker than unloading everything.