Running ZD1100 with 24 APs (half 7363 half R500) with 9.10.1.59 and 6 WLANS since release.
I don't notice any client problems (in relatively low density school environment). However do notice that ZD gui lags on refresh but liveable.
Think you would be fine on 9.10.
Still take note of the document recommendations as referenced by Charles V:
Disable all unused services, for example IPv6, Application/OS Detection, Rogue Detection, etc.
Ensure the L2 switches and the L2 networks are properly engineered to minimize the amount of
broadcast and multicast traffic seen by the AP.
With Mesh enabled, it is recommended not to deploy more than 6 WLANs on the AP
It is recommended to limit the number of clients on each radio to less than 70.
It is recommended to limit overall total client traffic to below 45 Mbps for unicast. It is
recommended to limit multicast / broadcast traffic to less than 5Mbps.