I DO like heal and try to use it when I can (which is not that often, I admit).
However, its main problem as I see it is that on most bosses and with decent gear, people are looking for HPS, which discredit heal. But if people are having a hard time with mana, heal is a good choice. Less mp5 and lower manapools could give it more importance in MoP, as its earlier importance in Cata.