that Ibis is an brilliant frame, and Ibis is a much missed company (yes, I know they're sorta "back" but they aren't doing the same thing as before)--I would guess it's more Ibis, than Titanium, that makes the frame so nice
there's plenty of crappy Ti frames out there--and plenty of brilliant aluminum frames
I would rather have a well done aluminum frame (ie Pegoretti Love#3, Cannondale, Ridley, etc etc) than a crappy Ti frame
the difference between builders, their techniques and quality of construction is where significant differences lie