Pros: Having owned the 24-70 2.8L for several years, for those of you wondering if it is worth the cash to upgrade I would say while not a night and day difference there are enough improvements to make it a worth while investment. The focus is faster, the lens is somehow smaller in overall size, but bigger in lens (old 77, ii 82), the colors definitely look better. It seems a little sharper on the edges than its predecessor. I was surprised that the lens hood is so much shorter than the original. The ii also has a lock button to keep the lens from extending when you are travelling between destinations.

Cons: No is.

Pros: Typical canon sharpness build quality and reliability. I have all canon glass and this purchase recently is one of the few lenses I didnt have to bridge the gap between the ultra wide and the super long stuff.

Cons: No IS.

Other Thoughts: I suppose the IS is not needed in a wider lens due to the focal length, but I can see it being useful at 70mm.

Pros: Over the past year, I have been continually amazed with the images that this lens produces! Being a professional canon shooter for over 30 years (as well as Nikon, Leica, hassie etc) wide angle corner sharpness has been a real challenge for me. I often have to shoot large groups of over 300, and although the 5d mk iii allows me to capture the detail that my medium format equipment did, glass to resolve the detail to the sensor has been a challenge.
This mkII 24-70 is among the sharpest lenses I've ever used. I performs as well or better than my zeiss 21mm 2.8 and any other prime available.
It's pricy but worth every penny. 200x's better than the 16-35mm 2.8 ii

Cons: Can't think of even one.

Other Thoughts: If you can afford it, get it

Pros: My trusty 24-105 which I've had since Oct 2010 is a hefty 670g but the new 24-70 f/2.8L II is even heavier at 805 grams! I've been lugging around the 24-105 so what's another 135 grams right?!? :) The exterior is beautiful. The black matte like finish blends nicely with the 7D's body. I love their new hoods that now uses a "button" that locks the hood in place and needs to be pressed to remove. Compared to the mark I 24-70, I'm glad they redesigned the barrel extension and the way the hoods look and works. I LOVE the new "lock" button which my 24-105 did not have. The extension barrel of the 24-70 is still pretty tight but over time it'll get loose so that lock button will be very helpful in preventing the barrel from sagging when I'm carrying it. The new lens has a larger lens opening at 82mm. My old 24-105 and even the 70-200 is the standard 77mm. So I had to buy a whole new 82mm UV haze filter. I decided to go with Bryan's (of the-digital-picture.com) recommendation and get the B+W MRC filter. It's pretty reasonable about $80 and what's another $79 when I just dropped $2000 for a lens right?!?

From what I've read, everyone was right, the autofocus on my 24-70II is smokin fast! Noticeably faster than my old 24-105 even in the low light indoors. I would say the focusing speed on the 24-70 f/2.8L II is even a tad faster than my 70-200 f/2.8L IS mark I!

But the one biggest factor that I wanted w/ this new 24-70II was the bokeh and the 24-70II did not let me down. Depth of field is just so easy to achieve with this glass compared to my 24-105. I can't wait to take some outside portrait shots. So far I'm very pleased with the bokeh... maybe not $2000 pleased, but still happy :) I keep telling myself it's an investment right?

I filled out the rebate stuff online which was easy to do. You just have to wait till you get your lens because you need to have the serial # of the lens for the rebate.

So far I'm very impressed with this glass. The price point is still very steep but as many others have mentioned, you get what you pay for. The 24-70 f/4IS and the 24-105 f/4IS is about $1000 cheaper right now. I've only really taken pics indoors without using a flash. Tomorrow I'm going to wedding and I'm going to use this lens on my stroboframe w/ my 430ex flash (my mainstay setup for event shooting in the past w/ my 24-105) at the reception. I'll also be bringing my 70-200 I to the church ceremony so I'll see what opportunities present themselves.

Cons: see comments in Pros