I used to use my SB600s/900s as part of a strobist system but became really irritated by the slowness of the recycling time. I had also used CLS, but the line of sight became a real issue during the daytime, and it becomes really frustrating when it doesn't fire and you're taking pictures of people.
Additionally, be wary to not overuse your speedlights. Over the years, I've burnt out my flash tubes around 4-5 times and had to send it in for a replacement. (Which thankfully happened under warranty). Furthermore, another thing I don't like is that the interface for changing flash exposure for Nikon speedlights is too slow as compared to an actual strobe system. This might not seem like a big deal but when you're on the go, timing matters.
With that said, I now use Alienbees. They're not expensive, you can get one for the price of an SB-700, and they are much more reliable for this sort of stuff than speedlights will ever be. Yes, its a little more to carry around, but I'd rather deal with the extra weight, than spending time worrying about burning out speedlight flashes, waiting for it to recycle, making sure it triggers, etc.
