With all the latest Xamarins installed on Mac and PC, Xcode 6 on the Mac, Visual Studio 2013 with Update 3 on Windows 8.1....
If I plug an iPhone 6 into my Mac, on the PC side of things, Visual Studio will simply say "No Devices Attached." Even if others were attached in addition to the iPhone. I have to exit Visual Studio, unplug the iPhone 6, restart Visual Studio to get the device list back. I can plug and unplug other devices (earlier iPhone, iPods, iPads) and refresh the list no problem. But if I plug that iPhone 6 in, boom, "No Devices Attached." On the Mac itself, however, Xamarin Studio does see the iPhone 6 without issue.
With the latest Xamarin updates, often when I try to debug an iOS device from Visual Studio, it gets stuck on "Starting Debugging session..." in the output window. The app has installed on the device, and is running, but Visual Studio seems to think it isn't. I can hit the "Start" button to begin debugging again, and often that will work. If not, I have to shut down Visual Studio and start it again.
"Connection to Xamarin Build Host failed..." shows up frequently, then just corrects itself. If it doesn't, clicking the message fixes the situation temporarily.
Xamarin.iOS on Mac 18.104.22.168
Build Host on Mac 22.214.171.124
Xamarin.iOS on PC 126.96.36.199
Xamarin on PC 188.8.131.52