Nikon SB-600 Speedlight Flash for Nikon Digital SLR Cameras

I'll be brief since there's a million reviews on this already.

Pros:

Works flawlessly with Nikon's CLS, often in challenging environments (in full sun, around the corner, where you wouldn't expect a good reception).
Great control from in-camera menus.
Simple navigation and setup (after a few days of practice)

Cons:

Obviously not as powerful as 800 or 900. There have been some situations where it's just not enough power; I've had to double up my SB600s or just rent something better.
I burn through batteries pretty quickly, but that's just the nature of strobing. Eventually I wised up and bought rechargeables.

I have a Nikon D80. I bought the Nikon SB600 to use as a secondary flash, as its description seems to imply. It does not work that way. DO NOT BUY THIS as a secondary flash unless you already have an SB800 or SB900. Sadly, I thought that Nikon products would work together better. I feel cheated and very disappointed by them and this product.

The flash works by simply putting it on top of the camera and it will do all the work. I particularly like the ability to bounce off ceilings and walls and still get proper exposure.

I won't retread older reviews with this. This flash does a damn good job, considering it's half the price of the 900. It won't give you all the reach or the coverage of the 900, but it does about 75-80% of what the 900 can do. What's more, it is about a third smaller, so if you're taking a fill flash outdoors it'll fit in a coat or cargo short pocket without falling out.

Light quantity is very good, and wireless response is excellent - from almost any angle, it'll respond to my D80's flash signals where the 900 sometimes won't. I use this both for work and for fun, and I'm not disappointed with it.

The only quibble I have is the lack of support for gels, but I know a lot of folks do DIY gels, so this is a minor issue. I would highly recommend this flash for any prosumer application.

SB-600 FlashNikon SB-600 Speedlight Flash for Nikon Digital SLR Cameras
I love this flash. I have a D300 so I have been using the built in flash but I bought this flash for more power and to use the built in Commander functionality of the D300 to fire this flash remotely for more flexibility and power. I plan on doing more painting with light and Macro photography so getting the flash off the camera is one of my ways to do so. You will need to buy a book or something to learn all about the power of this system. Plan for it and use it.