It is a sizeable upgrade from a TS-PC Racer. There are three really obvious things that are just better. It is really smooth, the feel is almost like a greased pole on a car and everything about the feel of the car is easier to notice and use. I especially notice that I feel dirt on the wheels if I dip a wheel as well as the bumps from the curbs and neither of these details ever came through on the TS-PC. I definitely notice understeer much more clearly, it was detectable on a TS-PC somewhat but not always but its really clear on the CSL DD at all speeds. Oversteer catches itself too on the CSL DD, it violently pulls and you just have to let the wheel go where it wants and its hard to get used to! It doesn't feel all that much stronger honestly but the FFB itself is a lot more refined generally.
All in all I am super impressed with it and I have barely scratched the surface in terms of playing with the settings, mostly just stuck with what Fanatec recommends.
I have run into issues in Raceroom with soft lock and wheel sensitivity issues and AC clearly feels a lot better than race room where before they felt fairly equivalent. I am enjoying my new fidget spinner anyway, clearly an upgrade from the TS-PC.