My game is about a 9 for me right now. As always, I feel like I'm DMing on a tightrope; I've never DMed a really high level game before, and it takes a lot of work for me to get the feel right. I am still trying to break out of the "one big fight instead of several smaller fights" trap that I've fallen in to. The politics have been really fun, though, and I love what's going on in the game.
I think my game has stayed at about the same level of fun over time. I can remember having this much fun (although with a different feel) back when the PCs were 5th level, so I count myself pretty lucky.
I still have bad sessions, though. I tried for one with a "whimsical" feel, and it rated about a "4" - tolerable, but not anywhere near what I was hoping for. You just shrug, figure out what you did wrong so you don't make the same mistake again, and move on.