Been running an MT-43 rear/MT-21 front combo and pretty happy with it overall. It climbs up stuff that's not exactly easy to walk up. However, with one exception of a front-end washout where the edge of the trail became very, very soft without looking any different, every time the bike has been on its side since I put them on has been on a steep, technical downhill. One of the biggest criticisms you hear about trials tires is their lack of braking ability downhill. That might just line up with my experience.
Now that I'm in a part of the South that's relatively flat and prone to be muddy, instead of the dry Cali mountains and desert, I got a set of Desert Race to try on my 610. Figured it was either that or the D908 on the rear, but WC's recommendations and the "I've never had a flat with a Desert" comment swayed me. Waiting for my cush hub rear wheel to show up to mount everything.
I'm also building an 18-in rear wheel for my YZ250 that will be a WR295 next time it runs. Will probably give the MT-43 a try on the back of that at some point if I head west of home where it's drier and likely to have more technical terrain.
Oh, yeah. Motul 300V 15W-60.
DIRT BIKES ARE FUN AND INTERESTING