My ex and I tried it out a couple of years ago for fun, and I only got one match (who wasn't him). Then I tried the sister site for same-sex relationships and was unmatchable. I tried that one again more recently and got a few matches, mostly interstate. Haven't tried the regular site again.
So yeah, I think I'm fairly unmatchable, though not entirely.
On OkCupid, however, I have a stack of matches in the high 90s

You have to find the site that works best for your personality.
The percentage thing doesn't really work all that well though... I have a bunch of high 90s and the few that do respond only respond once and then i never hear from them again...