I bought this last second before my first trip to Africa, which I had to bring on a Safari. It did not disappoint! There are a couple quarky things about it:
1. It is fixed at F11.
2. It requires “unlocking” to use.
3. Focusing is limited to a central area.
Those 3 things considered, this is the first you should get if you are considering the 600 and 800 f11s. The 800 is also great, but its bigger and doesn’t seem to be as sharp. This is a daylight Lens, but you will LOVE it for birding and wildlife.