I have a Maxxis Crossmark on the rear. Sucked to mount (I run Stan's Arch EX rims), sucks in mud, sucks in powdery dust or sand, weak side walls. Positives are high volume and fairly cushy (due to the weak side walls I suspect) for size. Otherwise meh. This is a race tire for World Cup courses I guess. And it is pretty fast for a tire with actual knobs.
I run a Kenda Karma in the front. Pretty much the same characteristics except I was able to keep all my fingernails mounting it, but it is impossible to run tubeless. The carcass leaks and leaks and leaks. When the carcass stops leaking that just means you're out of goop and you should expect the tire to be flat in the morning.
But I'm a stubborn butthead, I don't run actual tubeless tires, too heavy, you know, on account of having enough rubber not to leak air. :-)
"Why does the U.S. care which flag will be hoisted on a small piece of land thousands of miles away?" -- Ron Paul