Yet, there are quite a few. See the wiki: http://wiki.musl-libc.org/wiki/Projects_using_musl

A few big names are in the process of adding musl-based variants or switching entirely to musl, but most of these are still experimental. Alpine hopes to finish switching over sometime this year. Aboriginal Linux too. Bedrock Linux is already using musl in their latest release, but due to the way their distro works, they're in the unique situation where they don't have to build a lot of packages against the system libc, so they have it much easier.

I'm the founder / lead developer of Bedrock Linux, which as dalias said uses musl (as of our latest release). They've been very prompt about fixing any issues we have with musl and making it very hard to find excuses not to use musl.