I have been trying unsuccessfully to profile my device (via Instruments) using the latest version of Xcode 7.0.1 (7A1001 released 9/28), as well as the previous version of Xcode 7 (7A218), as well as Xcode 7.1 Beta 2 (7B75).
My device is an iPhone 6+ with iOS 9.0.1 installed - the latest GM release of iOS9. I am able to run / debug applications on this device without issues.
In the screenshots below you can see that my device is disabled (greyed out) in all screenshots in all versions. I am able to profile other devices running iOS 8.4.1 without any issues.
Does the current version of Xcode not support profiling against iOS 9.0.1 or is there some kind of configuration setting or known work around for this?
TL;DR - Perform a complete reboot of your device; restart Xcode & instruments; select "Open Xcode" if prompted to enable the device for development.
Update 3/31/2016: I haven't encountered any issues with the latest version(s) of Xcode (7.2.x, 7.3), so it seems that the stability here has been improved.
I believe I may have finally gotten this to work properly. Detailed steps:
As a side note, I was also again able to delete installed apps from the Devices window (I realized that this was not possible to do previously).
I'm unsure how my device ended up in this state however I will be on the lookout to see if this continues to occur.
Please note that this was done using Xcode 7.0.1.
Update: My device seems to lapse back into not being able to be used for profiling some time after performing these steps - I've had to reboot my device again in order for it to be available for profiling. Not sure what is triggering this behavior but I will file a Radar for this.