Anybody out there ever carb in the keg with priming sugar?

[Quin]

...but I've always thought the unsterilized priming sugar was just one more potential source of bacteria

Doesn't have to be unsterilized - bring a cup of water to a boil, stir in the sugar, and cover. Add it to the beer once it cools.

[spiderwrangler]

I've always thought the unsterilized priming sugar was just one more potential source of bacteria that could spoil my beer.

Boil it in a small amount of water... no spoilage concerns, and it will mix in better with the beer.

[calpyro]

I ether carb with sugar or by Krausening exclusivly. Both work good at metabolizing an O2 picked by dry-hopping or during transfer. Also, Krausening helps condition the beer quicker by reducing diacetyl and acetaldehyde in the keg.
I have found that my beer now stays "fresh" longer in the keg that when I force carbonated.

[mtyquinn]

The sugar is always boiled and cooled before it goes in the keg. SQUEAKY CLEAN.