I Run Kubuntu (15.04, amd64) in a second primary partition on the main H/D. I install Grub on this partition, and use a SuperGrub CD to boot it. This leaves the original 'doze booting when there's no SuperGrub CD, and also available with it. All stable and working fine - until Up?grade to Win10. That upgraded my Win7 fine, no issues. Then I re-booted with the SuperGrub CD in the drive - guess what? Boot straight into Win10! ARROGANCE! I have to use the Function key at boot to BIOS-select the CD. + + + Re-do from start +++ (Read some Discworld 
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Second issue: I use the 'doze for storage too - and need access from Kubi-wan. No probs? Not so! If Win10 is not shut down cleanly (easy to do - the screen is shut down before the file system is finalised
) the 'doze is left in an "unsafe state", and it won't mount.+ + + Re-do from start +++ again!
Moral: Wait for something that works. It's a faint hope, but M$ need to realise that computers are NOT just hardware to run their $oftware.
)Second issue: I use the 'doze for storage too - and need access from Kubi-wan. No probs? Not so! If Win10 is not shut down cleanly (easy to do - the screen is shut down before the file system is finalised
) the 'doze is left in an "unsafe state", and it won't mount.+ + + Re-do from start +++ again!Moral: Wait for something that works. It's a faint hope, but M$ need to realise that computers are NOT just hardware to run their $oftware.