I think it depends on the type of photography one is doing. Photojournalism requires quite simple equipment. But, if you are going to be photographing wildlife (say, birds) or sports, you better have a good lens with image stabilization.
What would you all recommend for birds? The last time I went for birds, I'd rented a 700mm, with results reminiscent of conservative political economics: there were a very few nice shots (of bear cubs, moose, anything but birds) and a great many very poor shots (consisting mainly of feathered specks flapping frantically out of frame).
-Dave
