Isn't the geometry of a tri-bike different from a standard road bike? A friend bought one and never felt right on the bike, and later learned "hey - it's a tri bike", and the design is different so that it taxes a different muscle set - or the same muscles in different ways - so that the bike ride, the run, and the swim aren't all demanding effort from the same components.
If the geometry is different, that's probably got to play out in things like climbing. Any tri-bike owners with an insight?