The good news.
The nice part of UEFI (Unified Extensible Firmware Interface) is that it is a safer more flexible way of doing booting. Instead of putting booting information in the master boot record, the boot programs are put in a special partition. This allows you to create multiple boot managers.
Also, you will hear a lot of scare stories about secure booting. While this is something to worry about, the good news is that it is easy to disable secure boot, and so that's not the major problem.
The bad news
Because UEFI is so flexible, there are lots of ways of doing booting, which makes it impossible to create a single standard way of doing things. Different vendors will have slightly different ways of booting which makes standardization impossible.
What I had to do to get UEFI booting to work on my ASUS laptop
- go into BIOS and turn off Secure Boot in Advanced
- Go into traditional BIOS booting by "Load CSM module"
- Install Mageia 3. I partitioned it so that Mageia was on my data disk
- Go into the BIOS turn off "Load CSM module" to off
- Use the Mageia Live DVD (Live CD hasn't got UEFI support)
- install grub2-efi via urpmi --root=/path/to/Mageia3 grub2-efi
- Answered yes to uninstalling grub2 (the non-efi version conflicts)
- Run update-grub2 create a grub.cfg file
- Mounted the EFI partition to /boot/efi, which for this laptop was located on /dev/sda1 (aka mount -t vfat /dev/sda1 /boot/efi).
- grub2-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=Mageia --recheck --debug (derived from https://wiki.archlinux.org/index.php/GRUB)
- Reboot and select boot from filesystem
- Fix grub2 entries for windows.
What didn't work
- EasyBCM doesn't work. I get the boot menu but it doesn't do anything
If you fail to set-up UEFI correctly, device may appear to be completely unresponsive (even BIOS or its EFI substitute cannot be entered), bricked (in case of several Samsung models, omit 'appear to', see here for example).
Disconnecting PSU+battery+(!)CMOS battery(!) usually solves this, although in two or more disk configuration (for example ASUS VivoBook S551LB) disk(s) without EFI partition must be sometimes removed for system to un-brick itself.
Also don't forget that on EFI-only system you should use GPT instead of MPR.
Opening your notebook to disconnect CMOS battery will most probably void your warranty.