Mine was at 9GB last time i checked and with all the content they are
Supposedly adding it will only get bigger.
Does the 12GB even have 9GB free?
Will be interesting how this pans out for PD, have they forgot about the 12GB model?
Edit, just checked 9971MB so 10GB!!!
https://www.dropbox.com/s/7amlur7lqfwxftm/20140117_064939.jpg
As for your other question:
If you didn't like GT5 then its doubtful you will like GT6.
The physics and loading speeds are the main positives but it still has the same negatives as 5.
New tracks are good, well, most are.
Only you can make that decision.
For all its negatives there are still the glimmers of excellence and that's what is so frustrating, it could be so much better with so little work.