My relatively new machine boots both UEFI and Legacy. I have tried Ubuntu, Fedora, and Arch in UEFI only boot and they all work out-of-box in their own ways.
Currently running Ubuntu 12.10 on a brand new HP Envy 4 Ultrabook. Everything works just fine, but I had to use Boot Repair and turn off secure boot in the BIOS before Grub would show at boot.
There is a special Ubuntu ISO for secure boot that contains pre-installed Boot Repair but it didn't work for me. I just used regular ISO and it worked like charm.
same here. ordered two Lenovo laptops and they were both allowed to switch between legacy and UEFI.