The Good: Keeps your chain on.
The Bad: Knocks when cage is pulled, cage lock feature is incredibly annoying, shifting is nothing special.
I now have used two different (short and medium cage) Sram type II derailleurs on my trail/slope bike (a Santa Cruz Nickel 34x11-36 gearing), and have the Saint m820 derailleur on my DH bike. They both do a great job keeping the chain quiet. The clutch did a surprisingly good job keeping the chain on. For the first two weeks I rode the nickel, I didn't have a chain-guide on it, and the chain didn't fall off once in 4 days of freeriding with 13' drops and all the jumps at Mountain Creek.
Everywhere else, the sram derailleur has fallen short. Compared to the switch that engages the clutch on the shimano- Once the cage is locked back on the sram, no amount of pushing the derailleur, bouncing the bike, or kicking it resets the cage. It goes back, but it is unnecessarily When the cage on the sram is set in place, there is a large amount of stiction on the clutch which has caused both my sram derailleurs to knock as my suspension compresses. Shifting was fine, but nothing special. The whole point of these clutch dealers is that they are silent, so why would I want one that knocks? And no, It's not my shock or anything else, its the derailleur. Sram's explanation- "Yeah, the clutch derailleurs don't always play nicely with full suspension bikes." As for the Shimano, I haven't had a single issue. The clutch switches seamlessly, and the derailleur is silent. It is worth noting that these clutch detailers require a lot more cable tension than normal derailleurs, and take a bit longer to set up.