Bit of an old thread but wanted to put my 2cents on the matter.
I had a wheel built up by Greg eariler this year, his quality of build is upi there with the best. The best parts in the world can be average with a poor wheel builder but greg is excellent and I am fairly confident in saying, whatever parts you choose they will be put together as well as they can be with greg doing it for you. If you ask for lower end parts it are the parts failing not his work.
As for the dh rims they are quite good, my last stock rim that came with the bike lastest me about 6months, I didnt retension spokes enough (i know) but the rim was buckled well and truely, with plenty of flat spots and I managed to put a few decent cracks in them, so far gregs wheels are running super smooth, spokes are still tight (be keeping an eye this time) rim has no dents or flat spots and the rim has not buckled like the other one did after a few rides. So far first impressions after a few months on the rim, It is resilient and stands upto more abuse than the previos rim, while been only slightly heavier it is a double wall rim compared to the previous single.
His turn around was quite quick too, I managed to get him around chirstmas and during a very busy time period just as nationals were starting, the turn around for my wheel was only a few days (2 I think).
I have not had tonnes of time on them yet but compared to my previous rims they are miles better.