I own 4 generators for three houses.
A 6.5Kw gas bought after Hurricane Isabel at my main residence in Virginia.
A "10KW" at the house I'm "renting" to my son and his family BOUGHT IN MAY 2015 (THANKS SODO!)
http://www.tractorbynet.com/forums/welding/336996-smokin-deal-10-000watt-generator.html?highlight=generator
A 12KW, (virtually unused before I bought it for $600 w/ a PTO shaft) Winco PTO in Mississippi.
And a little movable 1KW HF.
I was in Germany doing Army stuff for Hurricane Isabel (Sept 2003) and it's after effects, but SWMBO made sure I heard about them. Usually just after I got back to the hotel from celebrating Oktoberfest

.
Since then I've run the generator about every 3 to 6 months for about 10 minutes AND ONCE FOR ABOUT A HALF HOUR DURING A 6 HOUR POWER OUTAGE!!!
The Sodo buy was timely, about 2 months later there was a major power outage (where my son lives) for most of a week. I think a car knocked down a major transformer. Now I've owned that place since 1978 and that has been THE ONLY LONG DURATION POWER OUTAGE. And beside my son and HIS SWMBO there is a 3 yr old grandson and a 2 month old (at the time) grandaughter. He fired it up and it ran all the time, plugged into frig, freezer, a/c unit etc.
And the 12KW Winco I've only run to test it maybe 4 times.
So I've invested about $1,800 in three generators since 2003 and have personally used them for about half an hour. Now I have to admit I looked the I could read the future by supplying that generator to my son.
So I would say a PTO generator can be very practical. I'm looking forward to taking mine out for stick welding some gates. (Thanks to Shield Arc and the < $300 Everlast PA 300)