No matter what focal length you decide on...
If you are looking for a 70-200 it is hard to find a faster lense that this one
If I had the $ this would be in my arsnel:
This focal length is really practical and the performance of the lens is incredible due to the IS...so you may gain an extra .5 fstop...WoW!
Probably not the cheapest lens but probably if not the best and most practical focal length...
My 2 cents