Hi Dave. I run Product for Hosting @ GoDaddy and wanted to take a sec and answer your question plus give a little more color. I also work with the awesome Chris Carfi who already replied.

The Managed WordPress platform isn't a single server... it's a multi-tier platform with several layers of caching, many web servers and load balancers, and SSD-backed databases. It is shared hosting in that it isn't a dedicated box, but it isn't shared hosting like you might be thinking. This is a huge infrastructure with each piece optimized for the part it plays.

All that to say... all the plans have SSD-backed databases and many other things going on that you'll never get in a generic, shared environment.