I am relatively new to Paleo, but I do some IF that kicks me into Ketosis.
For example, yesterday I did almost a 24 hour fast not eating 7pm to 7pm except a couple of slices of salami. When I first started Paleo, which was the same time as starting CrossFit, I was seeing 1 pound per day weight loss. This dropped off after 10 days, but when I throw in a little IF, I see weight loss pretty similar. (Started at 202 in Nov. 2011 and I am currently 180 heading for 170). I have good energy through the day, and I do a morning workout so I am not too hungry when I workout.
Some people say that ketosis eats muscle, but my anecdotal experience is nice gains in strength doing the same workouts from Dec. to Jan. during which I was in and out of ketosis. Point being that if it was that detrimental to muscle I wouldn't expect to be getting better at my lifts.
Also, I notice that even though my weight isn't changing alot (muscle is heavier than fat right?), my leanness is changing and I see a difference there when I get Ketosis to kick in after a couple of days.
My last point, is that it doesn't take much to get out of ketosis, which is why I do IF. I follow strict Paleo almost 100% (had a little dark chocolate that had sugar in it last night). If I am in Ketosis and then have a bunch of fruit, then it takes a day to get back into it. Also, using Ketosis Strips tells me that I am generally only in the moderate range of 40-60 on the ketosis scale which is mostly impacted, I think, by fruit consumption.