i use the red band Nexus 8 on my crosscheck, but as a commuter and so far it is great at that job. too am interested in it's viability for cross as it is not affected by mud/chainsuck and it has a suitable gear range. I plan on trying it out soon with a bit of trail riding, i'll let you know what i think. It can be shifted with out pedaling too, pretty convenient.
Yes, it is heavy, I'm over it. That horse has been kicked. I weigh 218, a 21.8 lb bike is 10% bodyweight. How many 140 lb. guys ride 14 lb. bikes? What i mean to say is: weight is relative, and if weight is really your primary concern I'm sure that your quest for carbon and 200 gram tires would have overwhelmed any thoughts of an internal gear hub... they're just not that sexy.
Thanks to anyone who has any real world experience with riding a gearhub in cross races.
-Leo