I am quite happy with it. I had a Sigma 100-400mm that I got for shooting wildlife but over time I found that my Nikon FX 70-300mm was the lens I was using more so I sold the Sigma. I got the Tamron knowing that it might disappoint so I was prepared to return it if necessary. I was pleasantly surprised.I also had this lens but maybe I was unlucky as I found it very soft especially at longer focal lengths. I assume you are pleased with your copy?
I have since traded mine in and replaced it with a Sigma 150-600 which I am much happier with.