[Fourwings]

I can certainly relate to what you are saying Graham, I recently had a play with the Sigma 70 - 200mm f2.8 EX DG macro zoom and I was blown away with its quality, it was a fantastic lens, f2.8 across its focal range with a close focusing range of 1 metre at 200mm, it would make one hell of a good Dragonfly lens and dare I say it far more versatile than a prime macro, and still not too expensive at around £700.
Having said that I wouldn't part with my Sigma 150 f2.8 EX DG macro, the recorded fine detail is so sharp that you could cut yourself on it but I don't have to tell you that do I.

If money was no object I would buy the Sigma 120 - 300mm f2.8 EX DG zoom tomorrow, since having a serious play with this lens at last years bird fair it has left me in no doubt that this would be the ultimate multi-purpose wildlife lens, with or without the addition of converters.

In short, any lens that boasts f2.8 across the range is going to produce stunning results in the right hands, the only downside being that you have to part with serious amounts of wonga to get your hands on one!!