~ Distortion: not a real problem today. A series of software loads automatically correct deformations induced by the goal
~ Vignetting: 24 mm may appear if you add a little thick filter (polarizing typically), but it does not really bothered me until now
~ The focus tends to slide now cfr. if I put it vertically, he could spend 24 to 105 mm or otherwise that it is oriented according to the ground or the sky
~ Some say when dallonger zoom, there is a call dair that would go some dust: I am unable dobjectiver this phenomenon ...
For the record
In search of a quality material for a world tour of nearly a year, backpack, this is what i chosen as 24-105. The criteria weight and clutter were important. As well as the zoom range, to take both landscape (top with full frame) as portraits, etc. As for the resistance of the material, I can attest post: in tropical jungle in Asia, in tents in Iceland, in the cold at altitude in Nepal (the cup of water freezing in the hut) or in a bag in endless journeys on bumpy roads: back home, it is still one of my 2 boxes. And it's been 5 years it lasts. QED!
NB / to date, I lai used successively with a 40D, 50D and a 5DII