Not a hybrid, but my alum. road bike with a carbon fork and seatpost is very smooth. If you don't find a steel framed hybrid, you may want to test ride an alum. frame with a carbon fork and seatpost (seatpost can easily be added later). Wider tires on a bike can also be run at lower pressure, helping with a smoother ride. Might need to expand your search. EDIT--watch out for proprietary seatpost shapes, which if you need to change to carbon, could make it impossible or at least difficult to find one.