The potion cooldown was actually significant when I played the 09 demo. Something like 2 minutes, I think. Long enough to prevent using 2 in one fight. Seems reasonable to me. If you used a potion 10 seconds ago and already have 20% hp, you've done something wrong and deserve to wait around for a few minutes. Of course that situation seems unlikely. The fewer enemies, the less damage they will do to you, so at the end of a fight there was usually one or two unused health globes lying around to get me up.
StimmedMarine, Just know that unlike Diablo 2, Diablo 3 will have more deliberate combat. HP will fall at a slower rate, but with scarcer healing due to the limited potions, tactics and skill become important while having a boo-boo potion button becomes less so. So entering a fight with 30% hp will not mean instant defeat for a player that can play defensively and pick off weaklings until a health globe becomes available.
Q u o t e: Assume that whatever Grug says I agree with, so any loner he's arguing with instantly loses 2 to 1. -Cpslostudent