Lacking, but it has potential.
Railworks/Rail Simulator
There are many things that stops me on fully enjoying this.
Sway:
I remember it once had sway, a fake zig zag barely noticeable, I tried to increase it, but I couldn't find the code nor how to. A year ago, when Rs.com still had a forum in their website, they said they were implementing sway, investigating, they said they wanted to do it properly. They said it was hard to do it in 3d, and that is why BVE(before openbve came) was so sucessful, because it was in 2d. I always wondered because I've been enjoying some small company car racing games, they have "sway" or suspension, like World Racing. Even a buggy game like Boiling Point had vehicle suspension. So, how hard can it be to implement it? Now, a freeware program, OpenBVE implemented it, so successfully that it even has head "bobbing".
Take a look at this video, you will have your mouth open EVERY single second! I was, and some parts I couldn't even believe what I was seeing!
http://www.youtube.com/watch?v=QxgfhGZHznU
Headlights/lights:
I know, the UK doesn't use them much, but still, you can see the light "lighting" up the ground a bit in front of the train in the UK. But the problem is, the US, or the rest of the world, were they use it... MSTS, a simulator from 2001(but the coding much earlier than that) had implemented it successfully. I guess they could say that Railworks is a UK simulator, but they could use a system of dimming the light via a XML code. or some other thing...
But the "light" issue doesn't summarize completely on headlights, there is station lights, vehicles, semaphores and etc. Which should light up the environment . Addon producers have been trying to use it by using textures. It solves the problem a bit, but is not dynamic light like MSTS.
Editor/AI:
In Trainz I created various routes for my own enjoyment. I tried to do the same in Railworks, and it is much more complicated! Which explains why the addons cost much more for Railworks, it means more hard work in porting the model or creating a route. The AI has the intelligence of a highly hormonal teenager with acnes all over his face facing a conundrum of what to buy in a bargain bin of porn movies. (Porn you can always get it for free on the internet ... not like I know about it... or have 80% of a 100GB HD full of porn)
Sound:
It is still good, one of the things that still manages to save Railworks/RS from "oblivion", but it could be much more... I still feel bland, and it reminds me a bit of MSTS. But I still prefer the openbve/BVE sounds... It immerses me more.
Super Elevation:
They have a tool that you can individually increase certain parts of the rail to the height of your choosing, how difficult can it be to use the same code and modify it a bit to use it sideways? I mean...really, it can't be that hard! Even Indie dev's use it! I'm sure if I point out openBVE again someone will cut my head off....errmm... huh...hahaha... errmm openbve has it!
Patching:
I never had any problems with Steam, in fact, I love steam... I don't like to buy from it, because I'm a traditional person; I like to open DVD cases, smell that wonderful smell of printed manual( ). It is a great platform for patching as well. Why? Because it makes it easier to download it, instead of searching the Internet for a patch.
It has integrated browser, no need to minimize the game/simulator, friend lists and many stuff. I believe this was a right thing to do from the Rs.Com people.
Now, what they don't seem to understand is that, costumers are not their Beta testers, they should test more their patches before they release them on steam. From the many games I have in my steam account, Rs.com is the only one who looks like it doesn't test them.
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Beyond all that, what irritates me to no end, it makes me angry and sad at the same time. It leaves me "face palming" almost everyday is that the DEV's dont seem to realize they have a great product on their hands, they only need to work on it a bit more and add what the community needs, or at least add what MSTS already have(plus correcting the bugs). Maybe they do realize it, I don't know... Railworks needed at least 6 months more of coding.
I believe in Railworks, although I'm hugely disappointed in it, I believe it has potential, it has future to be one of the best Train Simulators around.
To show how much I mean what I say, I visit Rs.com, their blog, twitter and UKTS almost every single day, and sometimes multiple times a day waiting for a breakthrough on their part...hoping that somehow tomorrow they will launch a patch to correct its countless flaws.
PS: I hated that stupid flappy EcoDisc thingie...