My main gripe with the spell is that it requires a lot of attentive players.  Generally the druid casts it on a melee type, and then every time the druids turn come up he has to remember to alert the melee type who then has to add his 1 hp, and of course it is good for a DM to be attentive to all of this.  I find that by about round 5 the druid is sick of reminding the melee, the melee is sick of recording his 1 hp, and I am sick of paying attention to the duration.  Inevitably, someone forgets to tell/record/watch something and miraculous hps show up.  Good spell, annoying implementation.