I've had 2 wheelsets built up by universal. One was a 29" SS for my mtb, with 32h wtb dual duty freerides laced with butted dt swiss to surly hubs. The other is 26" 32h rhyno lite xl laced with 14g dt swiss to shimano xt rear/cheapest shimano dynamo front hubs. I weigh in the neighborhood of 240lbs, and while i did choose fairly burly components, i'm very happy with the build. I sold the SS, but put a lot of trail hours on it, never a hiccup. Still have the other wheelset on the LHT, no issues yet, but i don't have that many miles on them. Still, i've been commuting on them quite a bit, and i weigh enough.
So, yeah the build is good, and best of all, they don't charge for the build. If you buy all the stuff a la carte, it costs the same (but takes less time). So, as long as they have the rims and hubs you're after, you're golden. They do charge labor if you send your own hubs, fyi.