I've just purchased the Honda 2000 so I now have something for the small jobs.......
An 7 to 10 KW generator that will run off the PTO of my Kubota can be had for under 1500.
http://www.genpropower.com/w7ptos.htm
There are many others out there that are even less expensive. For me that seems the way to go. I don't want to spring for a complete stand alone back up system. My tractor is reliable and for now diesel is cheaper than gas. With 7 KW I can run the freezers enough during 24 hours to keep things frozen and keep us in lights and water the rest of the time...... won't be enough to keep the house cool in the summer but that is a luxury.... as far as warmth in the winter we have back up propane heat to keep the ice off......
Richard