Whenever I used to play, I hardly went on TS during normal games, because I get really bad lag and FPS due to a bad computer, and also, i found out that my Internet speed is bordering on dial-up, which is OK for surfing, but not great for keeping a steady FPS in games. Extra programmes like TS/XFire just slow things down further. However, I also keep it closed for another reason.

Every time I play in a scrim, at the beginning where the instructions are being given out by your SL over VoIP once you've set up your squads, there can be occasional snatches of chatter here and there on TS, which completely blocks out the SL's words. Then the chatter dies down and your SL says, "so that's the plan, it's a little complicated, but just do your best," and you're wondering what you could have done in your past life to deserve such a cruel twist of fate.

Basically, like some have said before me, TS just overrides any other communication trying to occur at that point. However, I agree with twiddilywink in the fact that if there is a huge problem, like you spot a squad on a back flag or something like that, and you don't have time to choose the squad you need, just blurt it out onto TS, and the closest squad to that can take the initiative to turn around. By first saying it on TS, you're letting everyone know something very important, then you can see which squad is closest and tell them to go there ASAP, but that first time you say it, gets everyone on their toes, and the squad that'll be turning back probably already know who they are. Also, apart from very rare pieces of information, most things that a CO would like to say should be quite squad specific. There's a squad making a break to the East, tell the Eastern most squad. A tank is making it's way to a flag, tell the squad closest to the flag. You shouldn't necessarily have to tell everyone at the same time more than they can already see on their HUD (tickets, flags, UAVs and Spotted by CO).