I'm looking to be corrected here so please feel free. I was on the Exchange 2000 JDP while an employee of a company with 80K mailboxes and the entire process was wonderful and exciting. We really looked forward to the benefits of staying ahead with technology.
Exchange on-premises today has become very terrifying territory that only consultants get excited about now. I don't know any company which uses Exchange as a resource (not Exchange dev companies) that would willingly risk their production data on these kind
of programs anymore. I'm actually curious about how a company could justify the benefits against the cost (since updates and rollbacks are much more involved) and risks for testing in a production environment. Many managers for mid-size companies (<1K employees)
that I've worked with in the past couple of years are pushing for the cloud rather than to trust a consulting firm and evaluating skilled Exchange engineering staff. Microsoft is currently competing two different technologies against each other and one side
is obviously losing.