Recently, I borrowed the Canon EF-24-70mm f/2.8L II lens from a friend of mine for a walk around shoot to see if it is worth my while to upgrade from the Series I model. My primary photography is Wildlife and Travel, in that order. Therefore, I have limited use for a zoom lens with this focal length.
The lens has an excellent feel, slightly shorter and lighter than its predecessor. It is fast, sharp and has great color contrast. It takes the 82mm filter, so for anyone upgrading from the Series I lens, you will need to buy additional filters unless you happen to own the EF 16-35mm f/2.8L II lens as well. The improvement to the Series I lens is marginal but the price is much higher. At a list price of $2,299, I find it hard to justify upgrading to the Series II, especially when the EF 24-70mm f/4L IS is just round the corner at a list price of $1,499.
If you feel you must have the highest quality 24-70mm f/2.8 lens on the market and you don't already own the Series I model and can afford this lens, go for it. However, if you want to wait a few months until the supply becomes more adequate and the EF 24-70mm f/4L IS hits the market, you might save yourself some money. Visit my website MichaelDanielHo.com to see photos taken with both of these lenses.