Check out Genode.org, MINIX 3, or QNX. Seem to have gotten a lot more done than Hurd despite being microkernel-based OS's. KeyKOS is one of the best from back in the day with EROS being a nice x86 variant of it. Turaya Desktop is based on Perseus Framework.

Many working systems in production from timesharing to embedded to desktop that are microkernel-based. Hurd and Mach's problems are most likely due to design choices that created problems.