[Klaus]

Well, IMHO the 12-100mm PRO is good enough for fulfilling high-end demands. From there on it's a question which other lenses offer a similar versatility in a smaller package. There are none.
Of course, you can always complain that it is too big but you either have to settle for less range or less quality with other options.

The combo fits perfectly into my small colt bag (Crumpler Jimmy Bo) - alongside with my purse - which is ideal for the city or short hikes.