Great Multi-Purpose Lens!

This was my first "L" lens. I bought it to replace my 5 year old Canon 28-135 which was first generation IS and starting to get noisy and vibrate.
The 24-105 seems to be a winner so far. There's a reason this optic costs $1000+ as opposed to the 28-135 which costs half that. Image quality is supurb, for a zoom. The overall build and zoom/focus rings are silky smooth. The Image Stabilization really lets you pull off some amazingly low shutter speeds handheld. This is a real boost since the lens is only an f.4, not exactly a speed demon. The nice thing is that somehow Canon has defied the laws of optics so that it remains an f.4 throughout its zoom range!