The major downside is it just doesn’t “feel” as responsive as a chain. I don’t quite know how to describe it, it’s not like there is a bunch of stretch in the belt or anything, but it just feels different in a way I don’t entirely love.

From what I heard, a belt drive has an efficiency loss that’s greater than a chain drive, so that’s what you could be feeling. The energy you put in isn’t being translated into the same energy output you’d get from a chain.