Hi I know there are lots of threads about which lens for walkabout etc and many answers that say there is not one lens that covers everything. I was looking to buy the canon 70-300 when I came across this lens that does seem to cover a good range but wondered will it be too big and heavy to keep on all the time? I know it is expensive at around £1700 but I could get rid of three other lenses in this range and just have this with my 10-20mm. Has anyone got one of these or had experience. Thanks