Running 29er revelations for about a year. I use the dp all the time and now wouldn't buy a fork without it. Mine are the solo air which I prefer over the double air reba's I had before. They also have the lockout/trail/full lever that I never use.
Great fork, highly recommended.
I serviced them a few months ago and they were very clean. No crap has got inside but I've been running a marsh guard which might have helped.
Only issue I had was when I first got them. Turned the bike upside down to hellitape. Spent about an hour doing it. Went out on a ride and they wouldn't work. Had a air lock or something. Sent them back and got the internals replaced (or so they said) never had an issue since, touch wood