The different versions of vSphere are Standard, Advanced, Enterprise and Enterprise Plus. If you are an existing VI3 customer covered by SnS and licensed for VI3 Enterprise you will be transitioned to vSphere Enterprise Edition.

If you then want to take advantage of the distributed network switch, use a third party distributed switch or host profiles you will have to upgrade to Enterprise Plus.

The different versions have different featuresets and limits. The table below identifies which feature is included in what edition.

Unless you have been living under a rock, I am sure that you have heard about vSphere aka VI4. VMware's is launching vSphere tomorrow and is quoting the event as "An exclusive peek at how VMware is bringing cloud computing to businesses of all sizes".

Blogs and twitter have been chatting about it for a while, I have remained quiet for a reason and that reason is that it is under NDA.
What is public knowledge is the impact it is going to have on Virtualisation as we know it which is going to be HUGE.
Twitter is going to go into meltdown.....

The event is scheduled to run via simulcast on the 21st of April @ 9am PDT, which means for most of Australia (syd+mel) it is actually going to be early morning wednesday 22nd, 2am to be precise.
Trust me when I say that you really need to be watch the launch or at least a replay of it.

We should also be clear about what the launch is, the launch is the release of the product information and featureset globally, not the actual public availability, known in the industry as GA.
A large number of people are very excited about the opportunity to access vSphere early on wednesday and that opportunity will not present itself unless you are on the beta program and in that case have access to it already.

GA is suggested to be a month or two after the actual "launch" of vSphere.

You can register here, and the event description is :

 "Join us for an exclusive peek at how VMware is bringing cloud computing to businesses of all sizes.

VMware is once again leading the virtualization industry by bringing cloud computing to the datacenter. Transform your IT infrastructure into a private cloud—a collection of internal clouds federated on-demand to external clouds—delivering IT infrastructure as an easily accessible service.

On April 21, 2009, we'll be unveiling how VMware is taking IT to new heights of efficiency, choice and control through service-level automation—dramatically reducing capital and operating costs and maximizing IT efficiency—with the freedom to choose any application, OS, or hardware.

Join Paul Maritz, President and CEO of VMware, as he and other VMware leaders officially unveil the next generation of virtualization technology from VMware.

Don’t miss your chance to participate in one of the most groundbreaking events this year.  "