I've managed to beat the game with all animals collected and no sacrifices!
Teleporting grenades, once you get the hang of it, is really satisfying to use. Being able to telefrag enemies with it is also very cool. However, not being able to cancel an existing grenade can be troublesome. Especially if the shot misses and needing to start from the bottom of the level again. Despite having so many creatures in my inventory, I never felt I had the need to use it. Perhaps the game was too easy, or there was no major incentive to use them.
Aside from some other minor glitches/bugs, the game is quite nice.