Hi all,
I started testing on El Capitan late compared to Yosemite - so the sixth beta is the first I've tested on my systems.
Since install, I have noticed that on the iMac (late 2013), the wireless keyboard is not being recognised by Windows. Interestingly, the commonest way I access my Bootcamp install is using Option-start, then changing from the default Mac partition to the Windows partition (using the keyboard), and then boot into Windows.
I haven't seen anything similar on my Macbook Pro which is running a Windows 10 / El Cap Beta 6 setup.
I followed the Apple support advice for 'keyboard issues': namely to re-pair the Keyboard on the OS X side. That went fine but hasn't changed the keyboard on the Windows side (not surprising I guess since the Keyboard works fine on OS X so is clearly paired correctly!).
I also used mouse-only with the on-screen Keyboard to find that Windows recognised the mouse and the keyboard, and was expecting to use an Apple Wireless UK keyboard - so there seems to be no configuration issues here.
Are there any known issues in this area (and of course workarounds?) I'm assuming it is the El Capitan install that has caused issues here in that I tested it a fortnight ago uneventfully without issue. Not filed a bug report yet as I just wanted to see whether anyone had any similar experiences (or indeed is happily reporting a similar setup working fine).