VSphere is by far the best, especially for bigger, resilient installations. HyperV is far cheaper, but not as mature, reliable or full featured.
That said, hold your horses for Server 2012 as by all accounts its far better than previous.
You're totally right about VMWares website, though.
Oh, and to be honest, if you're using ESXi without VSphere, then you're barely scratching the surface. Which is fine, by the way, but you do get a lot more functionality. Are you using a SAN, by the way?