I"ve had Truespace for some time, and its interface is quite different from the "standard" modelling programs.
The last I heard was that it was not being developed further - and that was about two years (maybe more).
It remains a powerful program, though.
However, to my knowledge, there's not been a "converter" to be able to use the Gamepacks, so it's use for flightsim modelling is limited.
I've used it mainly as a format converter at times.
For FS CFS2, you're pretty much limited to going through gmax/FSDS...