This lens is Canons highest performance midrange zoom and for just under $1200 this is a must have if you are just looking to buy general purpose lens. Canon announced this back in 2005 along with the 5d mark II. I am using this lens on a 1.6 sensor so the range for me is 38.4-168mm. This is my go to lens for just about every thing. It weighs in at 23.6 oz which is much less than the 24-70mm. The 77mm filter size is really nice because a lot of canon popular lenses use a 77mm filter. THis is not the cheapest filter size but being able to share filter with different lenses is nice to be able to do. The auto focus is amazing, Canons ring USM " Ultrasonic Motor " is very quit and rarely misses. If you are looking to buy a lens I would check out this lens. Remember you might have the best or newest DSLR that money can buy but if you do not have great of decent glass you are not doing your camera and justice.