I've been donig this recently to carb up my kegs.
Keg fridge full, plus I was out of gas (gulp) so full kegs were sitting out anyway, thought why the hell not, and chucked in 90g sugar (amount off the top of my head from reading) into a Pale Ale I was kegging.
about two weeks later, in the fridge it goes to chill down, and hook it up to tap.. light carbonation, and a real creamy head, that i'm guessing is from the keg carb and conditioning, that you dont get from out the gas bottle.
Great once you get full kegs, and ones ready to go, cos you can have an almost carbed keg, just chill and tap, and away you go.
It also lends itself to many 'samples' being taken to check carbonation levels once tapped..
I'm not sure about the 'half priming sugar' reason for keg priming - I need to do some reading I think to hunt down the basis.
thanks all for your responses and suggestions.
Cheers
:beer: