It's mouse-look that I absolutely love. The game just plays so much nicer with the modern control scheme.
If you're curious, the game's not fully working yet - iMuse isn't implemented, nor 2ndary fire and level 4 can't be completed. But the first 3 levels are fantastic and the bugs are being worked on.
Well, technically, this isn't a source port, which is better. It would allow the engine to do more things than the original engine ever could. This project will really soar once it becomes open source.