Also, to answer a question posed by Pedro a week ago now...
I looked up the Tribes website and the first thing that hit me was 'Most Difficult Shooter. Ever'. It's a bit intimidating - is there any room there for non-twitch players?
Tribes is actually the least twitch based shooter I've ever played. I think FPS fans call it the "most difficult shooter" simply because none of the twitch based skills that they've been honing for years matter in Tribes. Or, at least, they matter a lot less. It's by no means an easy game, but the mechanics are different enough from the standard FPS that I felt like I was on pretty even footing with everyone else learning to play for the first time.
Part of the fun of Tribes is that it has a pretty tricky movement system. Every player has a rocket pack that they can use to fly (thus building potential energy), and every player can "ski" down hills at the press of a button (thus converting potential energy to speed). With a little practice, you can easily fly/ski around the game's large maps at over 100 kilometers per hour.
It would be hard to hit such fast moving targets with a normal gun, and in Tribes it's harder still because most projectiles move much slower than in other FPS games. The game's signature disc launchers fire incredibly slow projectiles (though the splash damage they cause makes up for it), and even the game's more traditional weapons like chain guns and rifles require you to lead your targets by a huge amount if you actually want to hit them.
It definitely takes a lot of skill to zoom around the map quickly, and it takes more still to be able to chase a target down, predict his trajectory, and hit him with a well placed disc. These skills have very little in common with being able to outshoot an opponent in the half second machine gun battles that define traditional twitch based shooters though.
It's also free-to-play, so there's really no reason not to give it a try. Just be sure to join the "capture the flag" games, because that's really the game mode that Tribes was built around.