Short version: yes.
The last updates to Yummy and ShareEverywhere fixed a couple of minor glitches that I saw when running on iOS 9. To be clear, these versions do not use any new features in iOS, they just work properly with it.
Coming soon, both apps also have “real” iOS 9 updates.
ShareEverywhere 1.1.2 is a minor update, mostly to support iPad side-by-side multitasking.
Yummy 3.2 is a bigger update that includes the side-by-side multitasking, Spotlight indexing and a few other neat new features that are unrelated to iOS 9.
Version 2.2 of Rootn Toon is nearly ready to go, too. The current App Store version has a couple of minor visual glitches on iOS 9 but it’s fully usable otherwise.
Finally on the iOS side, I need to do more testing with CameraGPS. It seems to be okay, but with the same visual glitches seen in Rootn Toon. A new version will be forthcoming if necessary.
On the Mac, Quick Calendar still works well on OS X 10.11.
More information about each specific app when I submit to Apple.