I picked up an early 90s XO-3 from a CL seller last year, rode it around for awhile, and decided it was too hybridy for me. It felt sluggish, despite the 700c wheels, and I don't know if that was a function of its weight or its geometry. I sold it to someone who says he loves the thing, so there you have it.
From looking at those early B-Stone catalogs online
and the discussion on the iBob list
, it seems that there were a few different versions of the XO-3, with the earlier ones closer to the XO-1 in frame materials and the later ones (which is what I had) made of heavier cromo steel. I think.
I should add that everything worked wonderfully on the bike--extremely functional index shifting, excellent stopping power cantilevers--and it would make an excellent commuter or a good rider for canal paths and the like. Just wasn't the bike for me.