Would the gary fong diffuser be good for on the go snappy photography?
It's really like I said before Neil....the gary fong is great for portable usage. If you are just walking around without a real set of gear, just a camera and a flash..It's a nice tool to have with you.
You don't have to lug around umbrellas and studio lighting when you're just going for a walk in the park with a friend and you're using them as your subject...or whatever subject you may need the flash for.
It's nice, portable and easy to attach or detach if you don't want to use it.
But again, this is just my opinion, it really all depends on what you're trying to accomplish and what kind of picture taking you're going to be doing.
I like the diffuser and I stand by it, it's definitely been helping me for what I've been using it for.