Gautam,
I haven't bought the 2xIII TC. However, the 2xII TC finds lot of use especially since I am filming more these days. I am likely to get the 2xIII TC.

I didn't use flash. Don't like the look of flash in my images. The catchlight was because the tiger turned its head and caught the last rays. I was using ISO 320.

Cheers,
Sabyasachi