Just in the middle of a VMware presentation where someone has finally explained clearly where it fits in the grand scheme of things.
I understood that in larger environments, the ability to drop-in new hardware resources without requiring your technicians to deploy the OS on local disks (although that is pretty easy to automate) was supposed to be the primary appeal. Going against it is the lack of Service Console for larger enterprises who have fairly well evolved supervision and management toolkits that install in the Service Console.
Until today, nobody was able to explain exactly what you actually got with ESXi. I was completely lost with the questions of price and licencing and now I think I get it. The option for having ESXi 3.5 included with your new server will come either free or for a nominal cost. Start thinking about ESXi as the free replacement for VMware Server or Virtual Server. You get rid of the OS and for free (or close to it) you can do server consolidation on local storage. It remains to be seen if there are technical locks that block you from using remote storage or if that's done on the honor system. You manage the server directly using the VIClient, which is a big step up from the web interfaces for the current generation of free servers.
Each ESXi server in this mode is an autonomous server, but you can take advantage of all the really cool bits of the VI3 toolkit by buying Virtual Center and the associated ESX licences based on what you plan to use it for. So get a real free hypervisor (which is intended to push back the idea of Xen as a free solution) and a clearly defined upgrade path.
Side note - I like the new naming conventions. It's a lot clearer that Server denotes applications installed on a host OS, ESX includes the Service Console and ESXi is embedded. Although wouldn't "ESXe" have made more sense?