I don't dual boot but everything that I know about this process is that with Win8, dual boot or even with just Ubuntu you will need a UEFI enabled kernel on a Secure Boot machine even if you are only booting Ubuntu, and probably even if you have Secure Boot turned off. That means Kernel 3.8 or newer. There does exist reported machine specific quirks that the Kernel Devs will have to address on an individual basis. There are many posts in this section that suggest not testing on a Primary Box. I personally choose to ignore that suggestion but I don't mind a reinstall, its cheaper than a movie, popcorn and drink.