It is a trade off, between super detail and crippling frame rates. Obviously the more detail the more poly faces and then the slower frame rates. From the pics I have seen, IMO they have a great balance. Models are never going to be as super detailed as users might like; its all about compromise.
I think it is good they are holding back on the cab shots, it preserves some mystery and allows a big reveal on release. I was pleased to see Adam post a couple of weeks ago regarding the sounds. Steam sounds to me have always been a minor disappointment. A steam loco sound is visceral - you feel it as well as hear it, which just cant be replicated, but all in all, I feel they have done a great job; yes there are niggly things I wish hadn't been done, or had been done differently, but we are talking about a $30 game. Perspective...
Looking forward to getting a run. Now they have cleared these out, its time to start on the next PRR steamer for the roster (we do need more than 1 (IMO at least 3) )
G