Im going to start off by saying that I did a ton of searching on this and according to everything I have read, deleting the default admin user should be possible and should be done to enhance security; however it is not allowing me to delete it. I have a multisite install with 8 different sites running WP 3.5 and I ran into a multitude of issues while attempting to delete the default admin user:
1. With the original "admin" super admin, I created 4 new users and assigned them all "super admin" privileges. For some reason, even though I assigned them super admin privileges, I still had to go through each of my 8 sites and add all four users and set them as admins for them to see the sites in their "my sites" drop-down (which this seems like a bug or a much needed enhancement; all "super admins" should have access to the entire network as an admin by default).
2. I also went into each site and removed the default "admin" user leaving only my 4 new admin users. It is here I found another issue in that it never asked me if i wanted to transfer posts when i removed the admin user from each individual site. The user is no longer in the table (in the visual table, not referring to database table) however the posts still show as being written by admin.
3. I also noticed that when i was looking at all users for a specific site, the categorization links at the top listed "Administrator (4) | Super Administrator (1)" event though when looking at the network admin panel for all users, my four new users are all set as "super admins". Once I deleted the default admin user from the individual sites, the categorization links just show "Administrator (4)" now
I also set the network admin email to one of the new super admins I had created, as well as went into each site and through the settings I set the main email to the same new super admin user.
After doing all of this, I am still not able to remove the admin user from the Network users. Am I missing something in this process or did I just happen to find 3 different multisite wordpress bugs in doing this?