1 ACCEPTED SOLUTION
I got my EF 28-300L IS USM back in about 2011. It was second-hand but in good condition. The lens is the one of the super zooms that Canon brought out for their L series, if I recall correctly there was there was a 35-300 and one other. It is built like a proverbial tank, all-metal, heavy and with great optics, especially considering the range across which it was designed to perform. I am not a huge fan of push-pull lenses, but that was how that generation of lenses was designed: I had another lens from that era, the EF 100-400L IS USM that was also good for its time, but again push-pull.
I found the resolution to be excellent on my copy, and it focused very quickly, with good IS. It had a beautiful colour tonal quality about the images, one that I found only on a select few of the L-series lenses. It was with regret that I sold it last year to help fund my move across to RF optics, but I was downsizing my menagerie of DSLR bodies and lenses as I just had too many and having had a heart attack, I was suddenly aware of how much challenge a huge amount of legacy gear would put upon my family (who are not into photography) to deal with when I go. So, it sold.
I can only relate my own experience, but it was very, very positive.
The following image may indicated what I mean about the tonal quality. This was taken on an early morning walk, with the 400D (Rebel Xti), hand-held, available light. It is a memorial very close to where I lived on Vancouver Island to celebrate the life of a very brave young man, Terry Fox: Learn about Terry Fox. His life is commemorated in many statues and annual marathons across the county. 
I hope this is of some assistance.
