The Oil Drum

Of course ground source heat pumps are more efficient than air-source, but they are also a lot more costly to install.

I wonder if your figures for poor performance are looking at the very latest air heat pumps like this one from Mitsubishi?
http://www.wnibonline.com/pages/PRDetail.aspx?articleId=9302

They have been designed to give greater efficiency at low temperature than was available with earlier models, and also do a bit better with outsize radiators then the old ones, although of course not as well as they would with underground heating.
It is all a matter of trading off install costs against running costs, and having to supplement the heat on a few days a year by switching to electric is probably a better buy for many than having very high install costs.

As for the efficiency of PV panels between amorphous and monocrstalline, sure the latter is more efficient in terms of power by area, but unless you have severe space problems that is not the important metric, as panels are sold by their rated output.

And you are going to get more of that output on a cloudy day from the amorphous silicon, and they are also much better at producing good output when dirty or there are a couple of leaves on them:
http://www.solarvoltaic.com/images/doc/solar%20abstract.pdf
solar%20abstract.pdf

As for the preference for vacuum evacuated tubes for solar thermal panels, here is my reference:
http://www.viridianconcepts.com/Text%20Only%20Intro%20to%20Solar%20Power...
Introduction to Solar Power