Its true in practice, but like others have said, tires, grips and saddles play a large role in it.
I've never been on a CF bike, never been interested due to the big downsides you get along with the material, like dislike of having stuff clamped to it.
Titanium is a fairly nice ride, but i've only been on titanium a few times before. Its too hard to say how it stacks up to the others though, as the tires/grips/seat weren't constant.
The closest compare I can make is that we have several bikes around here, and the most comfortable ones are *easily* the steel ones. But thats not the only side of the story:
Steel #1 is a typical 1990's rigid MTB which has an Xtracycle on it, so along with having nice grips and such, wheelbase is extended, which also smooths out the ride quite a bit. This is easily the most comfortable one in the pack actually, with the big tires, long wheelbase, and good grip/saddle combination, there's almost zero vibration coming off the road, and it sucks up bumps. I'd rather tour on this than my touring bike.
Steel #2 is a classic 27" touring bike with gel/cork wrap on the bars and a properly fit seat. Very comfy.
Aluminum #1 is a "hybrid", and aside from Ergon grips, is uncomfortable. Vibrations on this bicycle are highly noticeable, but i'll be getting it some Big Apples someday.
Aluminum #2 is a full suspension all mountain Y-frame design. This bicycle is uncomfortable for extended periods of time.
Off my personal bias, aluminum is the only design that I find is not good in regards to vibrations. This may or may not be because of the material, but its because of the design: Aluminum bikes are made *not* to vibrate or flex, as that can ruin the material.
Last edited by Abneycat; 12-20-07 at 03:48 PM.