Still better than GatesMail
As any Lotus users knows, moving to Exchange is rather like swapping a sports saloon for a secondhand tuk-tuk. If you disagree then frankly you don't know what you're boring everyone about. But Exchange is moderately easy to install and maintain so there's at least half the reason why it is popular for half-witted/lazy administrators. So it's a popular choice, no surprise.
While Exchange is perhaps the model example of how Microsoft can come to dominate a market without creating the best product, it is good that IBM have not given up on Notes, and with the evolution to UC maybe the second wind will see Notes or Websphere or whatever the heck they call it now grab some land back from Email 4 Beginners 2007.