high availability is nice though not really required for a bunch of workloads. I mean I ran vSphere from about 2006 to about 2010 with nothing other than standard edition (no HA, no vmotion, nothing). Ran everything from Oracle DB servers to web and app servers, etc(all of the VMs if I recall right were linux). First couple years(first company) didn't even have vcenter. For a while in 2009 at least I was able to buy vsphere essentials packs and get the hosts managed by vcenter standard edition (vmware closed that license hole a couple years later)
I did have SAN storage though so if I needed to move a VM to another host I could do it(VM had to be powered off of course).
Back in 2008 before I left that one company my (new) manager at the time wanted to switch to Xen. He didn't even like paying the lowball standard vsphere pricing we were paying I think it was $3k for a 2 socket server for standard edition(excluding support I think). We got into a big argument about it at one point. After I left the company he directed my remaining teammates to start working on Xen (CentOS 5.x I think at the time which among CentOS 4.x and RHEL and Fedora we used as guest OSs). They spent about a month trying to get it to work and gave up and went back to Vmware. The core issue they were having at the time was the need to run both 32 and 64-bit CentOS guest OSs, and one of those(assuming 32-bit it was a long time ago) simply wouldn't even boot(mailing lists etc provided no solution). Didn't talk to that manager again for years but have since made up he apologized to me which was nice, and said yes (at least at the time)Xen sucked and vmware was better.
For the past 7 years or so at the current org everything is enterprise+, though I think the only real features of e+ that I use are VDS, DRS and host profiles. I'm probably a mix of a customer vmware would love and hate -- been using their stuff for 19 years now, very loyal customer(because of consistently good experiences) but at the same time not excited about any of their stuff other than the basics. vSphere 4.0 was the last product I was super excited about.