We went from 5.1u1 to 5.5 and has some hiccups with the upgraded process from the CD. Ended up with a complete re-install of the vCenter. It is highly imperative to read the knowledge base articles that were put out before attempting upgrade(s) of current systems.
VSC 5.0 is still not available, VSC 4.2 will still connect to vCenter 5.5, we use VSC mostly for backups, that is still working, but we do see errors on cloning virtual machines, have not had time to determine if it's a NetApp thing or a vSphere 5.5 thing.