Would anyone recommend the Sigma 100-300mm for Nikon D5000?

I have a Nikon D5000 and want a new lens. I have the 18-55mm and 55-200mm kit lenses but want a new lens and have seen only good things on the sigma 100-300 and by the pictures that people have put on flickr etc it seems to take good quality pictures. With this lens I'm looking to take pictures of sports, beach photos and portraits. Is this lens good for that and are the colours and sharpness good quality?

It's an interesting option. There's no doubt that it can out perform your 55-200 in every single way.

However for sports you may find that the reach is still a little short, you may find that the 150-500 gives a better range. Secondly this lens doesn't have OS (equivalent to VR), I would advise using a beanbag or monopod in conjunction with the 100-300mm.

Given the lenses that you have already, the 100-300mm has quite a bit of overlap. I recommend the Sigma 150-500mm. It will give you more reach, will fit in nicely with your current lenses and it has OS built in.

I have one on a D300 and am pleased with it.