Hello, I just wanted to add some details about what we've been doing with Alien Arena, and the CRX engine.
The addition of GLSL to CRX actually began in August of 2008, which on the surface seems simple enough, but as someone stated, it's one thing to add the shader support, it's another to make it do something useful. We were able to add parallax, normal, and specular effects to the map surfaces, as well as very nice dynamic lighting effects. After that we added new per-pixel water effects. The most difficult issue was getting normal/specular mapping to work on models, which took alot of trial and error, but finally we got that working about a month or so ago. This allowed us to remove the old fixed function per-pixel effects that were just horrendously slow, and not nearly as nice looking. It also forced us to completely rewrite the way meshes were rendered, which was a good thing. We are still exploring some other ideas with using GLSL for effects, and who knows what we will come up with. We are also looking at shadow mapping, and some other options.
I know when things get mentioned about graphics, people immediately think that is all that is being focused on, and that other things are neglected, but that is definitely not the case. Even though we've done alot of renderer work over the last year, we've also managed to work heavily on gameplay, artwork, and levels. Since the release of Alien Arena 2007, nearly every model and map have been replaced, which is something I don't think I've seen any other free game do in that timeframe. I really believe we have a remarkable little team in place that is devoted to their hobby. It was said in this thread that most FOSS games are held back by their art, and that Alien Arena was among those, but I firmly believe that our art assets are of good quality. I know that can be subjective and that is fine(and yes, I *am* biased

).
Regarding physics, there are things floating around in our minds, though I doubt they would come in the upcoming release, may down the road, such as ragdolls, and vehicle physics. Destructible enviroments? Possibly, well it's possible now, but not in a modern or cool way, but that could be something interesting in a deathmatch game I think.
The ultimate goal for us(besides having a blast working on a game) is to create an experience that is not only fun, but rich visually and aurally. I mean, if graphics meant nothing, we'd be playing Pac Man, right? It all counts, IMO, and no aspect of the game ever gets untouched between releases. We've done a lot of nice little things too, which will become more apparent when the release comes out, to make it just a more fun and pleasing experience.
Speaking of graphics, there is always a delicate balance of looking good vs playing good, and finding the right combination is often tricky. So to that end, we've steadily been optimizing, and at the same time adding various "eye candy" features. We've also made sure that the game is very scalable, so that people with older hardware can still play the game, which is often other dicey trick. You can very easily wind up bloating an engine trying to do that, so it has to be done with great care.
As for the future, and the other various similar games like Nexuiz, Warsow, Sauerbraten, it's really great to see these games pushing ahead, each trying to outdo the other. A little friendly competition is great(though in the gaming world that is another difficult thing to maintain, unfortunately). I don't know what the impending release of id tech 4 will have as impact. Most of these games are already making use of the same type of technologies, so I doubt many will be switching over. We saw the same thing with the other Quake engines. There were dozens of tech 1 engines, then when tech 2 was released, a handful of those. Tech 3 has far fewer, so I do wonder. I think most will attempt to glean some things from tech 4 rather than make a wholesale switch.