In some ways a bit of a stupind question perhaps, but I have rececently upgraded back to full SLR on a semi-pro basic. I bought a Nikon D80 with Nikkor 18-135mmD and then bought the Sigma 10-20mmD. I am now am looking at the Nikkor 80-400 which would ideally compliement the two lenses. Yes it has VR on it and that must be taken into consideration.

However, looking around I see that Sigma (for example) offer a 135-400 and also a 50-500 at obviously considerably lesser price. Now on an absolute level there will obviously be no comparision in quality but in relative terms is there really a great deal of difference?

I am often out in the country (on Exmoor for example) and having a good tele lens would be good for grab shots of wildlife.

What comments or suggestions does anyone else have please?

I have the Sigma 50-500 I use it on my D2x. Great lens very heavy,sharper and cheaper then the Nikon 80-400 vr. You might want to try the new Nikon 70-300 vr. it looks to be a winner

I have been into photography a good number of years and if I've learned nothing else "you get what you pay for."

I've had limited experience with Sigma (a total of three lenses from super wide to wide to telephoto), and I was disappointed with most. I found their telephoto range to be quite decent and cheaper than Nikon.

However, on the long run I suggest Nikon, since they are made specifically for the lens by the camera manufacturer, so you can't go wrong in terms of compatibility.