I really feel that the most useful thing I can do, having extensively field tested this lens, is to repeat and reiterate "Rich B's" crucial comment regarding using this fabulous lens with only one focusing spot.
There has been much criticism about softness, and even inaccurate focus, of the lens, especially at full aperture. Reviewer "Rich B" makes the comment, quite correctly in my view, that it is the minimal depth of field at wide apertures that contribute to this perception. All pros have their respective cons! You MUST focus accurately, even if you have to do it manually in complex situations. This will allow you to enjoy the rich Bokeh at wide apertures.
The other point I would like to make, is that image stabilisation CAN be a double edged sword. IS can be image rescuing when used correctly. It is very important, however, to remember that no IS system can eliminate fast subject movement at slow shutter speeds, a factor sometimes forgotten by some amateur photographers..... and remember, the very technology that allows IS to function, which is really beyond the scope of this short review, means that switching on IS can, in certain circumstances, actually INCREASE potential focus and lens performance inaccuracies. Image stabilisation, whilst very useful, is not a cure-all, and should sometimes be turned off! I'll leave you, gentle reader, to research the physics behind that statement!
Hope this helps and isn't too complicated.
Bottom line; even the finest technology needs the most powerful processor in the world, our brain, to function properly!