I have the coupe not the convertible, but I can tell you they do NOT feel slow. No, they are not the fastest cars on the road, but they are very quick, and have a good bit of torque which helps. The manual transmission is the same in the coupe and the convertible, it is not the smoothest, but you get used to it, and to make it smoother just keep the revs up, shift above 2,500 rpm and you will be fine. And the s2000 is fun but dosent have the torque the Crossfire has.

Hope this helps!