Well long-term resources in general are not especially the funniest thing around. I always thought "mana pool" was a stupid design in most games, and I still do. In LoL I really don't see the point of Mana in it's current state - if it was regenerating quicker out of battle, why not, but... Being "oom" is not fun for the oom guy, nor for the other, and there is no real gameplay leading you to force your enemy to go oom.
If you remove the manaburn mechanics, why not just remove mana ? That was the only mechanism that was giving a little interest to the mana mechanic - though really little, unbalanced and quite a failure from the start.
No, really, I don't see the point of mana in it current state. It just creates frustration - there is smarter ways to restrain avaibility of spells than mana (in its current state at least).