Marlin,
I bought my wife an Ulfrotte (which is now Wool Power) turtle neck top in the base layer weight a number of years ago.  These are my comments based on my observations:

Durability:  It seems to have held up just fine.  She only wears it occasionally now in the winter, but lived in it 24 hours a day during an extended trip in northern Manitoba and on sporadic trips since then.  It looks nearly brand new.  The weave isn't particularly tight, and there are little loops of fabric on the inside that seem like they would easily catch on branches, twigs, zippers, etc and pull.  However, this hasn't occurred based on what I've seen.

Warmth:  Heard good things.  Dries faster than pure merino.

Fit:  Seems good, though I think it has shrunk a little over time, even though it is washable.

Odor:  none, although my wife doesn't stink like I do ;D