This lens is part of the professional "L" line. It is not the sharpest lens in Canon's range and not the cheapest one. But it offers excellent value for money, nonetheless. The wide focal length range makes it a very useful lens, which can stay attached to the camera for most of the time.
Yes, some wide-angle lenses, some standard primes and some short telephoto lenses offer better image quality, but they require lens swapping or carrying multiple camera bodies with you. The main advantage the Canon EF 24-105mm f/4L IS USM is its suitability for a variety of shooting situations. It is simply a very good all-round lens, especially for travel photographers. Even though you could call it a jack of all trades, but master of none, I still like this lens very much.
In 2016, Canon released an updated version of this lens: EF 24–105mm f/4L IS II USM.
Below are some of my photos taken with the Canon EF 24-105mm f/4L IS USM.