Dale Vecchio has spent many years in the mainframe business, including 18 or so years with Gartner covering the mainframe beat. Today, he works as chief marketing officer at LzLabs, which recently conducted a survey with Microsoft on mainframe use.
The results may or may not surprise you depending on your views on mainframes. It seems that a very high majority of mainframe users would like to ditch their mainframes if they could. There are some other interesting results here as well.