I've oscillated between "worthwhile" and "hot garbage" on
Primal Command, myself. It's currently in my list, but lately I've been leaning more towards hot garbage, so it's on the chopping block. Jason swears by it, but he also swears by
Call of the Herd, so.
Birthing Pod is green, through and through. Trying to cast it and then activate it every turn for colourless is asking for a quick trip to Doomsville.
If you support a graveyard theme,
Mulch isn't the worst. I ran
Overrun - or something similar, like
Overwhelming Stampede - for four years (!), but I've finally come around to the stance that that category of spells isn't cube-worthy.
Revenge of the Hunted was sweet when I ran it, but I suspect it was always more fun than good, and I think
Setessan Tactics does the same job better. I'm currently experimenting with a small heroic theme, and
Boar Umbra is in there for a trial. I did get run over by a 7/7 umbra-ed up dude the other day, so so far, so good.
Last thing:
Mwonvuli Acid-Moss is the best green non-creature spell, and don't let anyone tell you otherwise.