I've been using spigots on my primary buckets for a while now. I put these together myself, but the set up looks a lot like the "siphonless fermenter" sold by Williams Brewing.
This set up "works," in that it makes sampling and siphoning a lot easier, and it's never caused an infection. But I'm finding that the seal around the spigot is extremely fussy. If I accidentally press on the lid or jostle the spigot, it springs a leak. Even when I've been very careful, I'll always find at least a small ring of dried wort around the gasket...evidence of a very slow leak.
I've taken all the precautions that are usually prescribed: using just one good gasket on the outside of the bucket, screwing tight-but-not-too-tight, etc.---but still I get that slow leak.
I'm wondering if others have come across this. Were you able to remedy it? Did you abandon the spigots altogether?
I've thought about putting keg lube around the gasket, but I'm not sure if that's sanitary enough for primary fermentation.