Sorry, I misread 1:4 as 1.4.no I was 100% certain this was a F/4 Zoom lens , its F/4 all the way though,
http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&fcategoryid=149&modelid=11924
its that one, I don't get the price...
That is actually a very nice lens, one I'd love to have (and will probably buy with my 5DMk3 when it comes out, or whatever other FF I eventually settle on).
The 24-70mm f/2.8 is obviously one stop better in low light (which shouldn't be underestimated, one stop is twice as much light). And they don't call that one "the brick" for nothin'...
But the 24-105mm f/4 is extremely handhold-able with three actual real-world stops of IS; as long as you have some degree of sufficient light the 24-105mm is much more versatile as a walk-around lens with a FF camera.
Personally I don't think it would be wide enough for general use on my 50D (or pre-ordered 7D), but that mostly has to do with they type of pictures I "see"; I'm either shooting macro or at the wide end and tend not to shoot much in between. YMMV.