I also have a 70-200 F2.8ISII, which I bought after trading in an older Sigma 70-200 F2.8.
The 70-200 F2.8ISII is on a par sharpness wise with my 300F2.8 IS. It is that good.
If you can afford it, then you won't be disappointed.
Another option to consider is the new 70-300L f4-f5.6 IS. It would be a good bit lighter than the 70-200 F2.8 & give you some extra reach.