Watching the first morning of the Australian Open on the BBC website (Safin vs Becker*) and I see they've started to use hawkeye in competition. Each player can challenge a call. If they're wrong twice they can't challenge any more until the next set. So far, I have to say I like it. It's allowing the players to focus more on the tennis and not get distracted by anger at missing what they percieve to be their point. Both players have so far challenged once and been right. I don't think they're planning to use it at Wimbledon this year but I hope they bring it in soon.
* No, not that Becker, Benjamin Becker. What with going down on the programme as B. Becker he tends to get big audiences :) He's actually not half bad but not in Boris' league.