Looking for a new racquet after my NS9000 just broke. I've been trying out my brother's racquets which included the AT900p, Arc 10, and MP100. I didn't like the MP100 because it was a bit too heavy; AT900P just didn't feel right, and the Arc 10 felt pretty good; NS8000 was kinda nice except a little head light which tired out my arm. Mostly a singles player. The NS9900 looks very promising but not sure if its worth the move towards. More of an advanced player with a good naturally induced wrist strength.
If you're an advanced player then NS9900 is a logical path to take. IMHO it feels a lot like a racquet which incorporates all the improvements that would make both the NS9000 and NS8000 better racquets than they already are. The NS9900 also has a balance point close to the NS9000s', and even the most head heavy specimens of the production batch will not be as head heavy as the MP100s'.
I don't know that a move to a stiffer head light racket is a good move if you already consider the NS8000 head light and didn't like it. I'd suggest looking at the AT900T or Z slash as well as the Arc10 (my go to racket right now).