I've just spend half a day trying (and failing) to install scvmm on server 2012 Essentials.
I finally managed to find the solution my self, so i thougt i should post it here for others to enjoy.
Problem: Installation fails if the server has updated to web deploy 3.5, which it does automaticly.
Solution: uninstall web deploy 3.5 using controlpanel/programs.
Reason: Very bad programming from MS...
Conclusion: don't ever install server 2012 Essentials, in a working environment, this has giving me nothing but headaches, the above is only one out of 5-10 similar problems i am and have been strugling with.