Are Hypervisor Vendors welcoming ISVs?

There is a great debate on which hypervisor vendor works with ISVs and which do not. You have a number of ISVs working with VMware that are just now starting to work with Hyper-V. A number of ISVs that are struggling to catch up in the virtualization space. Hypervisor Vendors that are directly competing with ISVs as well as welcoming ISVs. This story is not about any of this, but about how easy is it to launch a new product for each of the hypervisors available with or without help from the hypervisor vendor. In essence, is there enough documentation, community, and code out there to be interpreted as welcoming ISVs.