Having come back recently to working with VMs (it's been a few years), for my new startup in cloud computing (http://www.slicify.com), I was expecting that VMware would still be the leader in the field. I'd used VMware Server a few years ago, and was pretty happy with it.
Have to say I'm a bit disappointed with the current free options that are available - I only came across two: VMware Player (which has a crippled API), and ESXi (which I ran for a few weeks, but could never get basic things like VM cloning and migration working properly). I ended up going with VirtualBox, which has a much more extensive API, and makes operations like copying/moving VMs around so much easier.
I looked at a few others and wrote up a comparison on my blog: Virtualisation on the Cheap | Slicify @ Wordpress however before I write off VMware completely, would be good to see if I missed any other options?
(btw, I'm not trying to troll, just trying to get an honest opinion of whether VMware has a better free product that I've missed, or whether my experiences with failing to do basic things with ESXi are atypical).
thanks
Steve