I've just posted a picture in the off topic section thread on non retro rides. It's my current XC rig, a Lenz Leviathan 29er full suspension. I've built it up with some of my favourite parts. Another novelty for me is the 180mm cranks, picked up when reading up on the 29er forums. I have not corrected for the taller gearing here but I have a set of CD cranks with 20-30-42t ready for proper mountains.
I've ridden it for 3 weeks in anger now, some 120km. Both dry(ish) and wet with copious amounts of mud and some snow thrown in for good measure. Mostly flattish XC on mixed hardpack, woodland trails, mud and some loose sandy sections. The big wheels are a joy for taking obstacles, at every mudpool I take out 5-10 meters on my mates on 26". FLoat on the loose sand is as expected and allows me to really fly. On long drawn out high speed sections the momentum is great and the taller gearing helps.
In the tight low speed woodland singletrack section I do not feel any negatives on the handling. However, I did loose it and crash in a high speed double apex turn which I attacked "as usual". That could be the handling penalty of the bigger wheels, but I have since cleared the same section with minor line adjustments.
Bottom line it works really well for me in typical Dutch XC riding. As more mainstream brands are introducing 29ers I yhink it could really change the scene on the trials in Holland. Oh and the 180 cranks are keepers too.
Admittedly this is about 29er wheels and not about singlespeed and rigid steel. I do like the Singular a lot as I do similar style offerings from say On-One and Niner. But the US scene has some nice offerings like Curtlo, Badger and Vassago to name a few. And check out Salsa for some 29ers with clasic roots, choices choices....
Enjoy!