Dhruin
SasqWatch
Health is the subject of the latest update at the Diablo III site, where they describe the health globes setup. Apparently potions will be "moderately rare", so health globes will be important:
More information.That's where health globes -- floating, crimson spheres that rise from the corpses of your defeated foes -- come in. These globes are the core means of regenerating your health in Diablo III, and all other methods of healing support them. When you pick up a health globe, your health (and the health of any allies in your party) is restored by a fixed percentage depending on the type of globe you've grabbed.