I was hesitant about a similar set of wheels on another Trek, and a Gary Fisher. A person who works for Trek assured me that they are plenty strong, and would probably not even have a problem with my gigantizoid bottom. While I certainly think they would, the fact that they are THAT confident in their wheelset(s) says something to me.
Someone else hinted toward it, and I'll endorse it - it's never a bad idea to have a backup set of wheels around. I'd suggest talking to the shop and looking into having another set built up for you. The Sun RhynoLite is a popular 26 (and 700c) wheel. If it is handbuilt and laced up to a Deore XT hub, you won't gain a whole lot (but definitely you will gain some) of weight in your wheels. You could do 32h or 36h, I'd do 36h just to have a "tough" set of wheels around - you already have "light and supa-fast" covered with the stockers
Just as a comparison, I'm 360-ish and ride a Trek FX with a handbuilt 700c 32 spoke RhynoLite laced up to a Deore hub in the rear. I've busted one spoke in about 600 miles on it, whereas I had constant troubles with the stock rear wheel (also 32h). They are *tough*.