Is it preferred for a smoother start-up/idle when engine is cold? I'm in the Northeast if that has any bearing on whether or not to go with one.

 

not necessarily, the heated o2 sensor simple has a ground wire, battery pos wire and signal wire. Heating it visa vis the battery doesn't make it idle the car any better, it's more for using with race gas that contains lead. The stock sensor is prone to failure under extreme conditions and leaded race gas. The idea of switching over to the heated one is that you can just replace it with a readily available GM sensor at your local parts store for about 40 bucks or so, as opposed to the factory one that is 198 bucks or so.

 

I also thought the heated O2 would help, but if anything the car runs worse in the winter. It seems to run too rich when it is cold. I just go fed up and disconnected the power to it, then reset the stock cpu. I think you need a programmable cpu to take advantage of it. I think the stock cpu gets confused. Anyone else have experience with one of these things?