It souded pretty interesting. Here is the differences that I noticed from reading.
Small, basic infrastructure, far less code involved, new features are module-like and not added into the kernel
LINUX Monolithic Kernel
Large amounts of code, larger, features are added into kernel which increases size, lowers speed unneccesarily, and introduces bugs.
The other comparisons seemed a little skewed to leave out linux capabilities, or perhaps like they said, when they started, linux wasn't anywhere near how it is today.
Another thing was
1] Users can replace system services
2] No mutual trust to make use of other services
3] Security on the system is not harmed by trusting user services.
Doesn't that seem like trouble? Still not sure how it works, didn't see in the hurd docs. http://www.gnu.org/software/hurd/hurd-talk.html#the