No tags on objects.
Garage looks really nice: I've evaluated it with test code and benchmarks and it looks like a winner. Also, very straightforward deployment (self contained executable) and good docs.
But no tags on objects is a pretty big gap, and I had to shelve it. If Garage folk see this: please think on this. You obviously have the talent to make a killer application, but tags are table stakes in the "cloud" API world.
Thank you for your feedback, we will take it into account.