Neat game. It's a bit old school for my tastes, but I still enjoyed it. The mechanic of consuming enemies to get different upgrades is cool and leads to interesting choices about when you swap out for new ones.
One complaint is that essence being both health and the main resource leads to a rich get richer scenario. When you have lots of essence you can kill and devour your way through all the enemies. When you have none you're basically screwed unless you get lucky and find a safe path to vermin.