VMware vSphere Review
Ease of use, functionality, established product, works very...
Disclosure: My company is a VMware reseller.
Ease of use, functionality, established product, works very will with almost any prime time OS, very thought-out application, works with the developer community to improve, has deep pocket organization like EMC to help propel them into the future
Room for Improvement:
Moved away from local/domain end-user authentication to a single-sign on authentication mechanism, introduced a single-point of failure, added additional complexity that came be overcome with proper training