thanks for all your comparisons. They seem to confirm the best that one could reasonably hope from a 5x, reduced image circle zoom lens like the 17-85 EF-S:
a) It is better than its natural 35mm format counterpart, the 28-135 (same 5x zoom range, same angular FOV range), at least when are used with the smaller format.
It is as sharp as the 17-40 L (though with worse CA). Given that the 17-40 has the optical design advantage of a far narrower 2.4x zoom range, and is more expensive despite lacking IS, this sounds like quite a good performance from the 17-85.