Chocolate Porter

So after a couple month hiatus of brewing, I'm going to a brew a chocolate porter using some cocoa nibs from Theo Chocolate in Seattle.  (If you are ever in Seattle, check them out - they are truly awesome!)

I've never used nibs in my beer so this will be interesting.  My question to any readers out there is whether you have had better results dropping the nibs into secondary, or during primary fermentation?  Or do you prefer to put in at end of boil?

And roughly what amount of nibs do you use for a 5 gallon batch?

Thanks for any comments!