I installed the ZM when I was trying to find out more about Zune Reader, the official reading app for Zune HD. Be very glad you've never had to use it; I wouldn't wish it on my worst enemy.
There's hardly any useful information in the app descriptions, which is fun considering that some of the apps were for sale. The search function can't find an app by name. I knew the app was called Zune Reader, and the only reason I eventually found it was that I went through all the categories one by one. (With iTunes you can at least use Google to find an app.)
And the organizational schema for the Zune apps was divided into Games and Other, and neither category was overwhelmed with apps. I knew they had trouble getting people to develop apps for the Zune HD, but that really brought he point home.
I will not mourn the Zune, but I will toast the poor fools who worked on it.