Well, if you found it useful -like I did, and you want to go deeper in the field you'd then better go and check Eli's recent comments on the use of "quaternions".
From Eli's comment: "... I would use a quaternion based camera in two situations:
a) if the camera needs to orient in an arbitrary direction: ie any combination of roll, pitch, and yaw. Otherwise you can get gimbal lock. You'll have to web search for more information on what that is; I don't have the math background to explain it properly :)
b) quaternions also have the handy ability to interpolate between different orientations.
This can be very useful for third person cameras ..."BTW, read between lines: "... but like you guessed, we've been really busy ..."
... something is being cooked ... something is being cooked ... ;)