Cube had a new release this week, and I've been playing quite a bit of it. There isn't really that much that has actually changed, but there are quite a few new additions and tweaks.
The main "upgrade" in this release of Cube is the single player maps. There are a lot more of these puppies than there were in the last release, and the maps all seem to be very well done. There is a very Doom-like feeling that you get playing the new(and old) single player missions that no game now, free or commercial, seems to be capturing as well. It could very well be that most people figure that if they want to play Doom, they'll play Doom, but it's still a refreshing style of gameplay.
When it comes to the multiplayer, nothing has changed(which is good) but there are a ton of new maps. Some of the older maps have been tweaked or added to a little bit, so playing the older maps again is somewhat like seeing what's new in your old neighborhood. The new maps are very well done, and a lot more are making good use of Cube's heightmaps(Terrain) than in the previous release. The one thing that I would really like to have seen done to the multiplayer portion is in the player characters. Everyone looks exactly the same, which I suppose can help people from being ganged up on, but I think people would like at least some amount of character creation beyond picking your name.
Even though the one thing that bothers me hasn't changed, I'm still going to give this release a thorough workout. There are lots of little bits and pieces of niceties that I haven't touched on yet: Nicer animations, waaaay better death animations, and lots of little bugfixes and polish. One more nice thing: Cube was Slashdotted for it's new release, so you'll probably have no trouble finding people to play with online. By the way, for you non-Linux people, Cube is available for Windows and Mac OSX as well.