The ONE thing I desire most in Trainz is better sound!
I really dig (to use a dated term, showing my age :hehe

, the sounds trains make. I would love so much to hear all of them when I drive trains in Trainz.
The sounds we do have are mostly horrendous. That clunky junction sound, the lame click-clack.
I am now using RTS track for the rail sound. It is much better, still not perfect, but unfortunately the lousy points sound still comes through.
I would love to see more efficient code, so that I wouldn't have to buy a new computer just to enjoy Trainz. I'm still running an old P4 (single core) with 533Mhz DDR2 RAM. My video is OK (GeForce 9800 GTX+ 512MB), but any time I get into a scene that has more than one train, or is complex, I get ridiculously slow FPS. I have done some testing to know that it is my CPU that is the bottleneck, and I think that more efficient code would help.
I'm almost willing to pay for a copy of Railworks 2 just to listen to decent train sounds. Then again, it's still cheaper to go down to the real tracks and listen, record, and watch.
FW