Drinking potions in combat is tantamount to suicide, unless you have that delayed potion feat from complete mage. You provoke an AoO for doing so, waste a standard action (which can be used to attack), and the damage taken on this AoO possibly exceeds the hp healed (assuming it did not kill them outright before the healing kicks in, since the attack is made before they actually drink the healing potion).
At least the healing belt doesn't provoke an AoO when used.
5-foot step, pull out the potion, drink it. I am not advocating potions of course, but they may keep you alive for the extra round needed so you can get some backup, but I will state I am only drinking potions as a last resort .