You can tune it whatever way you want. You just need to setup the action and intonation properly after you do it, if it goes out.
It stays in tune really well. A lot of players are ditching their Floyds and going with Wilkies + locking tuners. I played a friend's guitar with that combination once, and I couldn't knock it out of tune no matter what I did (in a song context, I didn't hold it by the bar, Yngwie style).