I have the original non-IS 70-200mm f2.8, and despite what people claim it's a perfectly acceptable lens, even wide open. Sure, the corners could be sharper at f2.8, but the bokeh is good and you can stop down to f4 for landscapes....and the focus is very fast and the contrast is good.
That said, the lack of IS is a big deal. Even with this less-than-modern lens, softness from image shake is generally way more significant than softness from a lack of sharpness. The IS II will solve both these problems. Just get it and don't look back. But be prepared for a heavy lens.
That said, the original is no slouch despite its age.