Hey, I'm playing tremulous for like a week, it's a great game.
I was thinking that you should change the way messageboxes are displayed (by messagebox I mean the thing that appears when you get a message like the one telling there's not enough room to evolve there etc.). I think it would be better if you would make the message to be displayed in the top left corner of the screen (or wherever), with another color, and also play a short sound similar to a beep when such an error occurs so the player notices it. Because it is often that you get such messages, and it's pretty annoying to move the mouse to the "OK" button, that's why showing the message as an on-screen text would be better than opening a messagebox which takes time to close.
As for the windows (by window I mean the thing that appears when you build something or when you buy from armory) it takes pretty much to close/choose something. Noobs will, of course, click the building/weapon/item, read the description about it then build it. But people playing for a bit longer already know what everything is doing, so you should add a number for each building. For example, when the menu appears, have a number before each building name, like:
1. Egg
2. Overmind
3. Acid Tube
...
And, as an alien, you just press Q then 1 and it lets you build an egg (same for humans, just that it's with telenodes/turrets/armory/medistation/reactor/etc). Much faster. Also, you should add a key for the cancel button for windows. It sometimes happens that you are an advanced granger, and you want to attack someone, but you are used to attack with first click instead of second. You mistakenly click first click, and you get a building menu. Moving your mouse until the cancel button takes a long time, it would be much faster to just press ~ (console button).
So, when you mistakenly press first click, you press ~ (it's close to W,A,S,D).
I've seen pretty much talk on forums about binding keys, so I guess it is possible to do part of what I said by binding your own keys, but it would be much better that game would have it implemented, so everyone can use them.