First of all, it's fantastic that you have interest in M:R and would like to give it a go. It's been almost 9 year since the final version was released so it's great to see new faces to it.
A few things should probably be mentioned:
- While M:R worked to convert the Marathon 1 story to the UT engine, it is not meant to simulate Marathon in UT. As VikingBoyBilly said, there are differences between Marathon as an FPS engine and UT that make the experience inherently different. As such, it was an adaptation that was meant to suit the capabilities of UT, rather than force UT to be like the Marathon engine
- We've always wanted to clean up a few last remaining bugs with M:R, but we just could never get back around to it, for many legitimate personal reasons. The teleport problem in Welcome To The Revolution is documented on M:R forum in several posts and this one in particular offers a saved game to use to continue into Try Again
http://resurrection.bungie.org/forum/index.pl?read=8804
- Of course, I encourage anyone that has the interest, to try and play M:R. It's not Marathon in U:T, it's Marathon in U:T style. There are obviously subjective alterations to many things, be it models for monsters or weapons and it's unlikely that everyone will love all the ways in which our team interpreted the Marathon content. In addition to that, there were limitations at the time both from the capability of the engine (in U:T!) and obviously resources to get the project finished.
I hope that you do spend the time to get M:R loaded up and playing. Even if you only play up to the Welcome To The Revolution and not further, you'll still get a sense of what we tried to do and it should be pretty fun. Lastly, if someone you can get some people to get going on a multiplayer game, that is most certainly still a lot of fun. There's not much activity on the M:R forum, but maybe some people out there still have it installed and would fire it up for nostalgia.
Finally, personally I do feel that it holds up pretty well for its age. :)