I've done 4000k now on this bike - well, about 1.5k on the new frame, the rest on the old one. I'm really really happy with it.
I've done an ultra event last weekend - 420km / 3600m of climbing in about 14h - part of it through the night. The bike felt really really comfy. It certainly isn't slow uphill and it just rolls so well on the flat and downhill. I've put an 28c Vittoria Corsa on the back, which measures pretty much exactly 30mm. The front is a 25c which measures 28mm. Very comfy setup and still super fast.
At least on the rim brake frame, 30mm in the back is the limit IMO. You could put a 32mm in there, but it gets pretty tight at the rim brake mounts on each side of the seat stays. Clearance at the chain stays is still fine.