Ok, well, I'm on the server right now, and after playing for two games, I have some initial impressions of Tremulous 1.2, and they are both bad (sorry to be a downer).
For one, the Adv. Mara is WAY, WAY too overpowered. I know it's been said before, but still. The games have basically all ended with an adv. mara takeover. You should have to lead your electric zaps. BUT, if this is not going to be the case, lower the "firing rate" of the shock and lower it's power.
Second of all, the new mark system is a good idea in theory, but it's just so tedious. It's VERY hard to move a new building into a spot where another building already is without marking it, deconning it, rebuilding it, then marking it and rebuilding a new building that spot. Now, if there is a way to circumvent this, please enlighten me.
Oh, and there is one good thing. I like the enemy stagedown idea, because it adds a whole new level of "motivation" the the game.