In reply to Bojo:
I have a 9, and the in built stabilisation is top drawer.
I like gimbals (have one for my phone), and there are reasons to have one outside of just stabilisation (such as moving time lapse) but I wouldn't spend £100 just to add another item that has to be charged and can be broken into the chain, if all you're looking for is a feature you've already got.
Easier and cheaper to carry a spare battery.