I'd also add that the 6 oclock information from Vulcan can be applied to any direction with your hat. IE you can look left, left/back, right, right/back, up, and so forth, and still be able to move your head around in VR with the Rift, while keeping the hat button or KP mutton depressed. Most of the time looking left/right in VR, I find it to be just as fast and accurate as it was using TrackIR on a monitor, but further than the 3 to 9 line, personally I find that using the HTC built view hat/VR combination, is faster, and easier on the neck/back/whatever, especially when doing it fast in fights.
It's a great feature, one I think other games will copy in short order, as it removes one of the things that was a drawback (IMO, some sim pilots bang that "realism!!" drum, and think it removes some of that from the experience..), not being able to look behind yourself or looking in places that require a lot of head/body movement, at least not as easily or quickly. Playing PvP in some other games without this feature HTC has made, you really notice vs opponents with just TrackIR or thumb hats, they can keep you in sight far easier than you can keep them. With the capability AH3 has to combine view hats/key pad/etc with VR, it eliminates much of that disadvantage, at least IMO.