Not bad fora 170 bucks, you may want to try a higher f stop just to increase the depth of field a bit and it will most likely make the shots that bit crisper as well. Those lower light shots will stand an ISO bump to 200 or even 400 to keep the shutter speed up and you won't really notice it.
Love the cat shot and the last bird shot, the crop shows the focus is very good.
Have fun with it