A number of pro drivers on here so I'd expect a few 8s and maybe the odd 9.
If you consider yourself good simply for always being fast then you're probably a 3 or less. Good is taking account of the conditions, your car, weather, road and other drivers around you. Good driving is 90% observation and planning irrespective of your speed. Even that can't protect you from the unexpected (like an HGV driver falling asleep at 60mph+ behind you in slowing traffic or someone (two actually) stepping out into the road and your headlights without looking or warning - both of which I've had).
But despite being caught in a couple of major shunts I've never caused an accident or even ever caused any damage, still have a paper licence and have driven getting on for if not over a million miles (touch wood!!!)
Do I always drive slowly? Of course not - I've got a 3L, but speed limits are there for a reason so they deserve respect. Do I drive defensively? Absolutely! There's some pretty dangerous oiks out there. They don't give a stuff about you.
What does that make me? Probably still not as good as I think I am. I'd hope for a 7.