I finally got an event to use my new 70-200 II. Wow, this boy performed just as I hoped it would. I sat in the stands at a basketball game and put my bag in the seat in front of me to keep anyone from having their head right in my line of sight (it wasn't that crowded). I used my monopod setting down. The monopod took all the weight (and this boy is heavy), and I was very comfortable shooting, and I was able to get all the shots I tried for.
I did get some looks from other spectators, but no one commented.
The focus is fantastic. The light was good in this gym, so I was able to use f2.8, 1/400 on most shot, at ISO 3200.
I haven't processed but a few of them, but am satisfied with what I am seeing.
To answer the question of the thread, I will be using the lens for all events like this one and some nature shooting.
The remainder of the time (most of the time), I will use my 17-55 f2.8.
EDIT: I may not be using it that often, but when I do use it for events like basketball, no other lens would come close to the versatility of this one.