As an auditor, I find not enough people have this service done. Although I do offer it as part of any additional improvement that I make if its in line with the work being done. Currently I am in process of doing an insulation improvement on a home and am trying to convince the home owner to have the house air sealed. They truly do not understand the value of a blower door test and what air sealing means to them and are reluctant in having me do it.
People simply fall into place with all the bogus ads for windows and doors thinking they are going to save hundreds if not thousands of dollars on their investment. Or purchase shiny film materials to lay in the attic, thinking they are going to save money there. Yet a simple air sealing project can save them in some cases up to 45% on their energy bills without even adding any insulation at all. And combined with a blower door both before and after can see the results on paper.
I used a Green Realtor to help me find our house, and she offered a free energy audit (through a local company, not herself) with each purchase. It really helped us understand our energy issues when we moved in. I quickly did the cheap and easy stuff, such as caulking and sealing, and I think it made a difference on our energy bills. Of course, he had other recommendations that just haven't made it to our budget or to the top of the priority list yet.