People love that new lens. I wish I could even come close to being able to afford it.
I do agree that your sample images don't look very good. But at the same time your settings aren't very good for wildlife photography with a large lens either. I'm assuming you were working with some pretty poor lighting. The major one I see is your shutter speed. Way too low for wildlife. I like to shoot at around 1/1000 or so. Also, at f/6.3 you're not getting the most out of the lens, try jumping up to f/8 or so. I would suggest trying those settings on a better day with that lens before getting frustrated with it and spending a good chunk of money replacing the lens. I suspect with those settings in those light conditions you aren't going to be happy with any future lens you might purchase.