I'd say it depends if you have any little ones going along (if so this probably won't apply to you), your tolerance levels for weather & crowds, and of course the length of your stay...
DH & I were at WDW in late June 2001 for our honeymoon. We only had 5 days there, so we rushed sometimes & relaxed others. The crowds weren't too-too bad, but if anyone's used to winter crowds, it may be too much.
If you plan to be at the parks bright & early when they open, you'll probably get pretty much done by noon. That's what DH & I did, then headed back to our resort for a few hours to have lunch & relax & swim. Then we headed back to the parks for some sight-seeing, parades, fireworks, etc.
It was pretty hot & humid, and it did rain for a few minutes one day & then another day it thunder-stormed for a few hours so we missed Spectro & fireworks at MK (now a priority for our next trip since that was our last night there). I'd say if there's any fireworks that are a must-see for you, don't put them off til the last night of your visit, just in case.
As far as crowds/rides, we only waited a long time for 2 rides (Kiliminjaro Safaris/75 minutes & Kali River Rapids/45 minutes); everything else we went on in less than probably 30 minutes, most of which we nearly walked right on (especially with the help of Fastpass!). Since you're going for 8-9 days, if you can handle 90-95 degrees & some wait times, I'm sure you'll be able to get a lot done.
Hope this helps...Enjoy!
