Thanks Dave,
Ian, I looked at this lens before going for the 70-200mm f4L - the Sigma one was just outside of my budget at the time.
The review site linked gives this lens a rave review "highly recommended" and the MTF charts look like it will offer excellent performance across the zoom range - Go for it!
http://www.photozone.de/Reviews/Cano...report--review
Cheers
Doug
ps...Hong Kong ebay stores have this at a much reduced price to the one you linked to...
http://cgi.ebay.com.au/Sigma-APO-100...QQcmdZViewItem