I regularly bottle homebrew in growlers. I picked up some heavy duty growler caps from my LHBS. They are much different than the ones your local brewery will give you with a fill. To be honest, I don't exactly know why they are better/necessay, but they were cheap so I didn't argue.
The upside of bottling in a growler is that it is a great size to take to a friends house have a few people taste the brew. If I bring over bottles and let them pour, I tend to watch them like a hawk explaining why not to pour the entire bottle in the glass (yeast).
The downside to growlers is that I have often wanted to taste the progress of my beer during aging. This limits me by the fact that I don't want to crack an entire growler when a bottle would do.