You might want to also see the following url which has a lot of user reviews of the CZ.
Also last months Amateur Photographer had a big lens comparison test between the CZ and the Canon 17-85IS, Nikon 18-135 and a sigma and tamron equivalent which I cant recall. Basically they concluded the CZ was in a different league to all the others in every way except build quality. In fact its performance rating was better than most primes!
The only downside with the CZ is the build quality and ensuring you get a good one.