They're very temperamental, especially the snares, but if you can tune them well they sound great. Also much cheaper compared to other big brands. Their equipment is okay (they use Randall May for their harnesses now, which is a huuuuuuuuuge improvement over the XL days), the rims and construction make them stupid durable and STUPID HEAVY. In 2011, we compared our 28" bass 4 at Surf to Cavies 32" Yamaha bass 5, and the Mapex was heavier.
So, in short, if you don't mind goofy stands, you don't mind very heavy drums, and you have the patience to tune them well, Mapex is a GREAT choice.