I have actually used the Tamron 150-600mm (G2) quite a lot, as I found it sharp and easier to handle than the Nikon 200-500. I also liked the additional reach. Unfortunately, my copy of the Tamron has proven unreliable; it has gone off to New York twice now for warranty repairs, first for the autofocus mechanism and then for a sticky aperture. The Sony 200-600 focuses and zooms internally and is actually pretty easy to handle; my assumption (or hope?) is that the Nikon version will be similarly ergonomically superior to the 200-500. I understand what eaj101 says about this kind of zoom usually being used at maximum focal length. But there are many situations where suddenly one needs zoom back to accommodate a wider view; even if this is only for one photo out of ten or twenty, sometimes you NEED that flexibility without having to change lenses.
