First thing I had to do was to disable Fast Boot and disable Secure Boot. From inital power on, press ESC repeatedly until small blue boot menu appears, then select "Enter Setup". Goto Boot -> Boot Configuration and disable Fast Boot. Change boot order so that DVD is 1st. Goto Security and disable Secure Boot Control. Press F10 to save and exit. This allows the install media to boot (in my case a DVD). Install went fine, selected the "Install Ubuntu alongside Windows 8" option.
After install, the system booted to grub, but when selecting Ubuntu, screen would go blank (but not off) and all HDD activity would stop. Numlock/Capslock keys worked, so system was not hung. Pressing Enter a few times would cause HDD light to flicker, but otherwise nothing.. Ctrl-Alt-Fn would not do anything. Strange thing was that if I rebooted, pressed ESC to get blue boot menu, and selected the "ubuntu" option (created by installer), it would goto grub and then boot fine!
To fix this, I installed and ran boot-repair.
sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
sudo apt-get install -y boot-repair && (sudo boot-repair &)
I just selected the "recommended" option in boot-repair. After doing this, I had to add another boot option as per the instructions - had to add sda1/EFI/ubuntu/grubx64.efi. Pay attention to what it tells you, as it may not be identical, depending on your partitioning.
Reboot and press ESC on boot to get blue menu, Enter Setup, goto Boot -> Add New Boot Option -> Add boot option and give it a name (i used "ubuntu13.04"). The filesystem was pre-selected for me, the path for the boot option I entered as follows: fsx:sda1/EFI/ubuntu/grubx64.efi - have no idea what the fsx: is about, but it was given in the help text. Scroll down to Create, and press enter. Press ESC to go back, and then move the newly created boot option to #1 position. Reboot and enjoy. Fully functional dual-boot system with Win8 and Ubuntu 13.04.
Why the Ubuntu folks don't learn from the boot-repair folks is really a mystery to me...
NOTE: I ended up having to delete the Windows 8 boot option in the BIOS, because after booting from grub into Win8 once, it did something to bypass grub.. frikin Windows!