My whole life growing up I was taught that Kia and Hyundai were bad cars. And once upon a time they were. But like Kia and Hyundai, Tamron and Sigma had the same stipulation. It was until I started selling Tamron Lens, that I realized how their new G2 and entry level lens were much better than people claimed. Below is a photo I took with my Tamron 18-400mm F/3.5-6.3 Di II with Vibration Control. I paired this with a Canon 7D Mark I.
I was about 30 feet away from the bird and lied on the ground to capture this image. I lined the goose up with the bridge in a vertical orientation and shot this at 5.6 aperture. It still produced more than enough separation from the foreground that I like. Here is another shot at more of a wide angle with the same camera/lens combo.
In short, this lens has a great value to your collection. In particular, if you are currently using kit lens for either Nikon or Canon, this would make all of those inferior. You can sell your kit lens on eBay, purchase one of these from Tamron, (with an included 6 year warranty), and make your camera bag weight and size a lot more condensed. Keep your eye out for upcoming specials on this lens around $599. Purchase only from authorized retailers and make sure you do not purchase a grey market lens or camera.