I'd be interested too. I have none, and I think it's hurting me a lot in arenas. I'd be interestsed in seeing what people are doing to handle targets in Arena - Gladius or the built in system. Other things I'm looking into:

Cooldown alerts - need to know when TS is ready, and grounding totems
Who's casting what - rezzes and CC's should pop up a big message.

What are the top arena teams doing now? We're only 1505 at the moment, but we're facing the same 1800-2200 cleave teams over and over, and I know they can be beaten (we've done it before).. we just need the tools.