Not that this matters much any more, but, I have never found hibernation to work properly, so I have always disabled it. And with it costing $3 a month, I dont see a point in worrying about it.
Btw, just so others who may not know, running 4 gigs of ram on a 32 bit system will only make use of 3 gigs. But, I won't recommend 64 bit version of vista. Too many app conflicts. Until manufacturers both (soft and hardware) get on board there will be more issues than its worth.
At least thats my opinion, from what i experienced.