Hrm... I remember seeing some research her eon the forums about that...
It way that the XP bonus should go is something like (Base*Rested)*Quality or so? (that is mathematically the same as multiplying everything? god I think I totally mistook something but it's more or less add rested tobase and then do quality on top of that)
But at the initial levels where I'm getting only one god-forsaken leve for all of six levels on ALC... I've noticed that I get a lot more XP with Rested