I'm looking seriously at a Bianchi CC but have a couple questions. First. I'm about 5'10" but have a 32" inseam and am wondering if I should get the 55 or the 58 (I'm going to use the bike principally as a road bike, w/ a little off-road). I like the general comfort/geometry of the larger bike although it may be less than ideal for serious off-roading. Any thoughts? Any other thoughts/comments on alternative X bikes for consideration would be much appreciated. Thanks!

I'm just a hair under 5'11" and have a 32" inseam on a good day, and I couldn't go any larger than 55 on the Axis, and wouldn't want to. It's one of the handful of bikes I've encountered where I didn't need to change anything to be comfortable (except to get rid of the gawdawful WTB saddle).

and they measure C-T so the 58 is more like a 56. my 61 (I'm 6'4" 35" or so inseam)
and I ride the 61 Cross Concept. The TT is 59.5 like a 59-61 roadie but the ST is 58 or so.
I think a 58 may be too tall for you as it's S/O is 32.5. The 55 may be short in the TT butjust get a longer stem.