My first few days with 70-200 f/2.8L IS II - Constructive C&C most welcome!

Hello fellow photogs,

I recently picked up the Canon 70-200 f/2.8L IS II and have been spending quite a lot of time shooting with it. The gallery linked below contains photos taken exclusively by this glass and I'd welcome some constructive criticisms!

In terms of my impressions with shooting telephoto, I must say that I'm enjoying it immensely, though I do find that, between f/2.8 to f/4.0, it's a bit tricky for me to get my subject in focus, especially when I'm at or near 200mm. Correct me if I'm wrong though, but I'm sure this is just a part of shooting telephoto at f/2.8

Next time, I'll bring a monopod or tripod, or just stop down a bit more.

Thanks again!