I love the addition of the hopper support for composter outputs. I feel that it only makes sense for hoppers to be able to feed in to it as well! That way composting can be automated with large farms rather than needing to spam-click the block.
Also, I saw this mentioned somewhere else, but I agree - bamboo should be a compostable item!
I should also mention this would help for large scale conversion. If I have 18 stacks of kelp, I don't wanna stand there for 15 minutes - I could put it in a chest and walk away!