I have this lens and it's the lens I'm most likely to take with me on a trip
I find it a jack of all trades but master of none type lens , the focal range makes it verstaile and the VR helps in lots of situations , it's not too big or heavy either.
It is not as quick to focus as most of my other lenses , it has a bit of distortion And light falloff, but these are easily fixed in Post production.
The image quality is decent enough , it's not tack sharp but not overly soft either
It's F4 so not ideal for low light but depending on your camera body you could ramp up the iso to compensate
Having owned a canon 24-105 I would say they are on a par with each other
Basically this is a versatile lens that can be useful for many things but will have its drawbacks if you compare it to other lenses
If it was me I would keep the tamron and buy or rent this lens to compare them and see which I preferred, I like to have the extra reach and VR which is why I haven't got the nikon 24-70 and for low light I whack up the iso or take a fast 35mm out