I've had my copy of Sid Meier's RailRoads for several days now so a few observations.
I've worked my way through most of the manual although I don't regard myself as totally proficent yet.
This program hogs memory and will tax your PC like no other. The program will crash unless you are proactive and setup your program and PC of optimial running.
I had to replace my current Nvidia drivers - not for the faint hearted and reinstall.
My current PC has 2 megs of ram, and a 350 gig harddrive it's about 6 months old and it just about runs this program.
Railroads is'nt quite as good as the orginal Railroad tycoon, (IMHO) play isnt quite as complex, but it does run very well.
Routing is handled a little differently, trains can't double back on them selves, so you have to design your track layout to suit. Industries are similified, and there no buying of hotels at stations. Rather buy industries. The graphics as you would expect are superb. I've only tried the one player version so far as this is a great way to learn how it runs.
Would I buy it again - YES I Would