I had same dilemma but nevertheless upgraded few days after release - why? Cause I love to work in Cubase and it’s my professional tool for work. You should see the money Adobe users have to pay for their software 
It wasn’t new features that made me decide but more of the stability and performance tweaks. Once upgraded, liked the new zone feature and mixer undo is great. Also, transition from 8.5 was very smooth.
Anyone that has concern about upgrading and spending some money - yes, C9 is the most stable and bug free release so far. Alongside new features you’ll get 5-10% gain in performance.
Steinberg didn’t let me down with C9 as it did with bugs and terrible GUI issues in version 8 (fixed later).
Sure, one could wait for the trial to check your system stability, but so far I had zero problems 
For quick VST/CPU performance comparasion between 8.5 vs 9 check this thread: