Let's see, we have FreeBSD, NetBSD, OpenBSD, and Solaris. Two of them have even been integrated in current GNU systems (Debian/FreeBSD and Nexenta). How does yet another kernel help?
The irony of this remark is that while it is literally correct, the truth of the matter is that Hurd is stuck in the early 90s and aims to re-implement a 20-year-old design.