I got my UX21A three days ago and there are some issues, using Ubuntu 12.04...
Since, there are reports of similar (if not the same) issues on UX31A, this thread should address these two models...
* some Fn-Keys do not work
* keyboard-backlight won't turn off
* Power-Key doesn't show Power-Menu.. it does nothing instead, when pressed..
(* wifi disconnects often (but signal is very good!), latency is sometimes very high (up to 1000ms, but only on 802.11a - 5GHz)) -- might be just an issue for me...
* brightness sensor (does ubuntu already handle those kind of data?)
* keyboard-backlight turns off after closing lid and go to standby
* standby doesn't always work when closing lid (then you have to use the Suspend-Fn-Key...)
* power saving is not quite perfect, I only get about 5,5~6h of battery life (using same tweaks as for UX21E)
* there are random freezes, once or twice a day, using latest (and earlier) shipped kernel of Ubuntu 12.04 (linux 3.2.0-26), this issue is not present in Kernel 3.4 and higher (using mainline kernel 3.4.0, but power consuption is ~1W higher (equals 30 minutes!) with this kernel)
* incl. USB-LAN-Adapter
Not tested yet:
* suspend do disk
* incl. VGA-Adapter
Now, do you have any idea, how to bring these Fn-Keys to life?