I have Railsimulator and enjoy it. Basically the same thing.
The good:
Route building is ALMOST as easy as Trainz, still a little quirky though.
Excellent graphics that run smooth as butter where Trainz stumbles for me.
The bad:
AI is still a mess, a train due several hours from now locks it's path preventing you from switching any turnouts it needs.
North American content is not very plentiful but can be found. Quite a bit requires payware to work.
You're stuck with Steam even if you order the DVD.
Automatic updates from Steam wipe out any mods you make. More than one has been caught off guard.
It has it's points though and can be enjoyable. It's also a work in progress so is continually being updated. There are few over at Train-sim making some headway with it. Scanning the RW forums there would give you more info on it. I usually fire it up when a get a little burnout going and need a break from Trainz and MSTS. I would get it but I'm pretty much anti Steam so stick with RS. That would change if they get the AI straightened out.
Dave.....