Right now my server is on VMware Server. Too lazy to migrate, but otherwise I would have switched to Xen many decades ago.
I mean... do they really expect people to pay for ESX or whatever after they have tried the free VMware Server??!
Sluggish web-only interface (opening the management console takes about 2 minutes, and every page about 1 minute to load - server is unloaded and on LAN), where a simple operation like "adding a new datastore" would take half an hour due to freezing/"operation failed"/reloads. Very buggy "remote console" (for viewing the guest screen, as a browser plugin), crashes all the time on Linux, sometimes won't load on Windows... I seriously think they would do much better without VMware Server, instead of letting people get this kind of first impression.
My advice if you want to try it - just don't. Not worth the time.
I am going to switch to something else, anything else, next time I reinstall my server. Probably Xen.