Shantanu: Great image quality, excellent VR, however it's rather slow to focus. Not an ideal choice for sports or bird photography.

Jeff: I used this lens on a safari trip to Kenya. I wanted the longer reach of a 400mm, but didn't want to break the budget on some of the faster lenses. I used it on a D200 and focusing speed was mostly ok (but agree trying to capture birds in flight might be a problem). There is a focus limiter to help, but I didn't use it. I will say you should take a practice day to figure out the situations you can hand hold vs mounting on a tripod. I'm usually pretty good at hand holding, but found it challenging to get a nice crisp image at full zoom. We even had to turn off the safari van when using this lens as the vibration of the engine running was killing the shots. I understand the sweet spot for aperture is between 9-11 and tried to keep within that range. I got some nice shots out of it, but it wasn't as consistent as I had hoped. I might try one of the faster high end lenses next time.