Ben,
I have seen several of them for sale (new) on eBay in the last month, so there are some cheap(er) ones out there. I can't think they are hard to install. It is just a remote readout of the DDEC system.
Jon,
I like the 69.9 MPH figure since I still get to run with the cruise on, everyone passes me and the driving is less stressful. And I still get 5.6 mpg. When I bought my first tank of $3.00 diesel, I threw the notebook away and just enjoyed the ride. I would rather not fret over the $ per mile and just ease down the road with the King of Bling getting smaller in the mirror.
You fly to Oshkosh for the same reason a dog licks his nuts