Hi Jock.
That lens is now 'quite old' and somewhat 'outdated'.
Tamron introduced a much sharper IMAGE STABILISED version (i think they call it VC on Tamron lenses) last year and there are some excellent reviewsonline . I have the VC version myself as a walkabout lens and it's a heck of a lot lighter and cheaper than Canon's L 28-300.
One for sale at AVForums for only about £90 more than the non VC version you pointed to. Good luck if you go for one, they are excellent lenses.