I have probably about 3 hours of gameplay so far, so not as much as many, but enough to have some initial thoughts.
I'll preface this by saying I've never really been able to get into US freight operations, despite having lived over here almost 15 years. So, I didn't really buy TSW for enjoyment per se, more to see what the new engine offers and to support development. So I won't really comment in detail on operational interest, other than a couple of general points.
Personally I haven't had any performance issues having run TSW on two systems - my laptop (5th gen i7 with a GTX980M at 1920x1080 resolution and all settings on ultra) and my desktop (6th gen i7, 2xGTX980Ti in SLI (which I know the Unreal engine won't use, so basically only a single card) running at 4096x2160 with everything set to ultra). Everything is very smooth with no stuttering at all. My only observations would be two-fold; TSW seems to be very GPU intensive even when paused, I left it on pause on my laptop for about 15 minutes and it was running pretty hot. Second, leaving TSW paused for any length of time caused performance problems (I left it paused for about 2 hours, came back and it was an unplayable slide-show).
Generally, the graphics are a step up from Train Simulator, though there a few niggles. Anti-aliasing is still poorly implemented and looks blurry no matter the setting (other than off). There is some flickering of textures in the distance (at first sight, very reminiscent of the z-fighting Train Simulator suffers, but it seems to be limited to more distant scenery and is so less obvious). Telegraph wires look pretty rough, they fade in and out with distance, even at 4k resolution (this may be related to the anti-aliasing, which I'm not convinced is working as intended). Lighting, to my eyes, looks a little flat and washed out, but its a new engine and I may just need to get used to it (and this may be configurable / tweakable). Overall, it looks good, for me not a huge step-change over recent high-quality Train Simulator routes, but there is a lot of detail. Track to scenery edges are a huge improvement, and the skies look much better.
I really like the tutorial system, its very effective and nicely done. The new HUD is also great, a massive improvement. The HUD could use a speed limit / signal display, similar to that in Train Simulator (or, personally, better yet like the old mini-HUD in Rail Simulator), but on the supplied route, that's not too important. My only issue is that I can't get the in-cab touch screens to work (for example the tutorial where you set the slow speed, I just can't get that to work on either of my systems, there's either something up with the interface, or I'm doing something wrong, which isn't good in a tutorial!).
The "out of cab" experience is kind of a novelty, but one that's already grown old for me. While it's neat to a point, personally I think it's also a bit unrealistic (isn't that why there are two people in the cab, so the driver doesn't have to do EVERYTHING?) It would be nice if either the second man (whatever the correct term is) got off his backside, or there was an option to just skip external activities, personally I would find it more enjoyable. It's nice, and its original, but sometimes I'd like to be able to just skip it...
I haven't had a chance to play in surround or with my headphones, so I'm only using monitor or laptop speakers, but so far, generally I'd say sound is a minor improvement over Train Simulator, but nothing to write home about.
I think its a great start, certainly much more complete than Rail Simulator was back in the day. There are a few niggles, and areas for improvement, and I'd certainly like to see UK routes and stock to really capture my interest. I don't regret my purchase at all, and I think the future is bright. It will be interesting to see what the developer tools look like, and I'd like to see a timescale for that sooner rather than later, as that is really going to hold things back. I'm also curious whether content development for TSW will realistically be within the grasp of the enthusiastic amateur, or if it will be practically limited to professionals (given the level of detail required).
Bringing Merseyrail 1980 back to life, slowly...