I personally love that lens, BUT everything we shot was outside so YMMV. It was one of my favorites for quite some time. A lot of people like the 24-70 more, mainly because it's faster, but I had some issue with the one we used (seemed a little soft, but that could happen to any lens).
I had carried my 24-105 since 2006 almost on a daily basis, until recently it failed a few times. I had it repaired by Canon, but not sure it was really fixed, I sold it back to B&H.
It's one of the most versatile, professional-grade lenses. Now I miss it a lot , and will buy it again if it's bundled with the replacement of 5D 2. For shooting video, I believe 24-105 is far better than Canon's 24-70 due to its IS and extra sweet focal lengths of 85 and 105. The difference between f4 and f2.8 is small, almost irrelevant nowadays - I realized that after i started to shoot all the way to f1.2. The difference between f1.2 and f2.8 or 4 is big.
This has been my "go to" lens for over a year now shooting events and travel. Works great for still photos and is extremely durable and versatile. With the amazing high-ISO performance of a 5Dmk2 the slower f/4 aperture really isn't as big a deal as it used to be. For creative DOF use you will probably want to go with a nice prime f/1.4 anyway.
I've used it as a backup to shoot video on location, mostly B-roll or when I didn't have a real video camera on me. There are three issues with using this lens for video:
1. The IS stabilization is designed for still photography, not video. It does not compensate much compared to say OIS on an HVX, and tends to jump around quite a bit which is not at all ideal for video. Apparently the VERY new Canon L lenses (100mm L Macro?) are using a new IS method which is designed to handle video better.
2. The focus drifts significantly when zooming. The footage is often still usable but it will be soft at the beginning or the end depending on where you chose to focus.
3. The zoom is not linear. Rotating the zoom ring at a constant rate you will find the wider you get, the faster it zooms out. At the wide end it is zooming VERY fast with very little travel.
All in all it's one of my favorite lenses by far and the IS is a lifesaver for perfectly sharp indoor photography. Well worth the money.
It's a fantastic lens especially for the kit price.
I actually prefer it over the 24-70 for one reason alone: IS. IS is critical if you're shooting video, more so than another stop of light. If I was doing photography, 24-70. If the 24-70 had IS, i'd go for that -- but it doesn't. Being that it's my most used lens, I think it's absolutely a great thing to be included in the kit. I don't know about the above poster, but the IS in mine works great for video.. I don't have any issues with it jumping around. I guess that's the thing about these photo lenses in replacement of cinema lenses/ compact primes-- I betcha the $50,000 cinema lenses canon is beginning to offer doesn't vary lens to lens, at least not nearly as much.
That said it's a great lens and 90% of my shots are on that. I'm actually considering selling my 70-200 f/4L IS (I'm not a sports videog and have found little need for that range). It's an excellent range and the 5D can handle up to 1600 iso (Specifically that, has to be multiples of 160 to be clean) so f/4 isn't much of an issue.
Well I like the 24-105. I don't care for F2.8, mostly because the 5D is shallow enough at F4-5.6...2.8 is a nightmare. Even if I had the 24-70, I would likely be stopping down most of the time anyways. The IS helps too as others have said.