Love this game. Great job. Great effort.
Music: 5/5
Awesome, just awesome.
UI: 4/5
At first I thought this to be a 3/5, but the tooltips help. Also, the game improves on X-Com:UFO Defense's UI greatly, adding in all those things I wished for. The Geoscape view wants to be more "Google Earth" like, I want to be able to grab earth and spin it around. Also, it took me a little while to figure out how to man my drop ship and equip my soldiers.
Graphics: 4/5
Quake II, not a bad choice! I'm not a developer so I don't know what would stop you from using Source, but maybe it started before then. In any case, it's major leap forward from the original. I got sick of DOSBOX limitations and the thing slowing down when I blew up a building.
Story: 5/5
I actually read all the flavor text in the emails from the lead scientist. I like it, it's actually more immersive than X:COM.
Gameplay: 3.5/5
Again most of the changes are welcome additions. Some of the maps have places that look like you can walk on but can't. That's really weird. It took a good 20 minutes to try and figure out how to cross a stream on one map.