[ilya]

I disagree, I think calling on the flop is the right play. You don't have all that many chips invested in this pot yet and you can definitely afford to fold on the turn if another heart comes. I think waiting until the turn allows you to get out cheaper if you have to, protect your hand against a flush draw + pair combo that could call all-in correctly on the flop, and get more information with your raise.
Also...if your opponent calls your flop raise without a heart, and another heart comes on the turn, he might sense your weakness and bluff you out on the river. If, however, he calls you without a heart on the turn, and the fourth heart comes on the river, he'll be less likely to bluff you because you won't have shown weakness at that point.

If you hadn't made the pot bigger by raising preflop, raising on the flop would be a better option. That's not to say that I mind raising preflop, but if you're gonna do it, raise enough to narrow the field. As it is, you're asking for a big, multiway pot -- not what you want with this hand.