I have a (build-in) board in my Acer V3-571G laptop with the switch to activate/deactivate UEFI in BIOS.
With SL X (KDE) Daily Build from 27/12/2012, I was NOT able to boot from USB-memory, when UEFI was activated.
The error message was: No UEFI media found (in this case I activated 'Boot from USB media').
Means: My BIOS was not able boot from SL X live system on my memory stick.
Solution was to deactivate UEFI-Boot in my BIOS. Then my (unchanged) memory stick was found, and I could boot from and install from.
When I created an SL 11 memory stick live system, I made the same probe.
I activated UEFI-Boot in my BIOS and booted with my plugged in SL 11 memory stick.
There was no change, my BIOS couldn't find any (external) UEFI media to boot from.
Now, I have an ssd with only 2 partitions, 1 for swap and one for SL X, always updated since 27/12/2012.
My Windows 7, I have installed in a Virtual Box. I don't see any benefit for Windows 8.
With my laptop was delivered a 750GByte 2.5 inch Sata 3G disk, which I disconnected, and keep it for later, when I will sell my laptop in about 2 years. The preinstalled Windows 8 is not yet touched and not yet installed on that disk.
It is brand new and not used.
My conclusion is, when a linux partion is already installed on a media in a laptop/pc then you can't change it from 'No-UEFI to 'UEFI' then.
And in case you use a have already installed Windows 8 with UEFI, I don't know, how to boot from SL 11 live system USB-stick, because the BIOS doesn't recognize it as (UEFI) bootable.
This is only my experience. If there is any way to boot from SL 11 live media with an activated UEFI in BIOS, then I don't know it.
But as I said, I don't need Windows 8 and for the rarely cases I need, Windows 7 runs in a Virtual Box.
To answer your question to use SL X and then start many updates. follow Rigo accurately with updating config files also. And you could boot later, provided, you won't have activated UEFI.
I am really not sure, that a new GRUB 2 from SL 11 will really manage UEFI on an installed system.
The main proove would be, that we can definitely boot from a USB memory stick with SL 11 on an activated UEFI BIOS.
Hope to help you, anyway.
-Linuxfluesterer (I love KDE ...)