You wont regret getting the Bigma. I love mine, I did flirt with upgrading, with disastrous results. I'll stick with the Bigma for now.
I tend to try and shoot at least at F8, at the 500mm end it's a little soft at F6.3.
As many here will know, I don't use a tripod. I use a mono-pod for most of my Bigma shots, but you can use it hand held, especially for flight shots where you usually will have plenty of shutter speed to play with.
Here's a few tasters for you:
Flight shots:
Darters:
Heron:
Good luck with yours, don't be surprised if it take a little time to get used to the lens, especially if you've never used a large lens before.