I've used LEB128 (with canonicalisation) extensively and... this looks so much nicer for most use-cases (length prefixed, supports the full uint64 range without that extra 10th byte).

The downside is the encoding size. LEB128 quickly grows to 2 bytes, but stays at 2 bytes all the way to 2^14. This is important if you're using these numbers as tags/identifiers as we were in the multicodec [1] project, or for network message lengths. bijou64 only gives you 500 <= 2 byte numbers.

[1]: https://github.com/multiformats/multicodec