Ok, very low compatibility as far as I've tested. I've got to work as mentioned, daedalus, gpsp, nesterj and popstation.
however no luck with mame4all, cps1, cps2, mvs. I've tried on CPS2 from latest to 1.66 , both 1.0 and 1.50 with no luck. I won't try any more versions since they will lack too many features to be worthwhile.
I think source code for CPS1, CPS2 and MVS emus is available so hopefully someone can take it and compile it again with the m33 tools and make them work on slim.
One thing, if you can't get emus to work, even those that are confirmed to work like daedalus r12, format the ms. I got nothing to work until I formatted the ms, don't know why.