The Crossfire isn't blessed with the smoothest shifing tranny that's for sure, it does take some getting used to. If compared to practically any car from Japan, you will be dissappointed. I agree, even the Viper shifts better most of the time too.
Usually it seems the more it warms up, the better it works, but not always.
I usually never try to down shift into 1st. without going into 2nd. then into first.
At 30k miles, I had the transmission oil changed, and for some reason, it seemed to become even more notchy "after" having it done.
I drove a friends 05 roadster, and his felt very smooth, so I really can't say why some shift better than others.