I'm running Ubuntu 11.10 on ThinkPad X220.
Browsing through the ThinkWiki pages I stumbled upon this information:
Multiple monitors
Configuring an extended desktop over two monitors led to malfunction. Side-by-side worked, one above the other did not.
In natty the solution was just to avoid the layouts that caused the malfunction.
The problems appear to have been completely solved in Ubuntu 11.10 (Oneiric Ocelot).
Has anyone of you managed to make X220 work with a dual monitor setup? Does it require UltraBase? Any special tweaks or modifications?
It works but it is unstable. For example, if you hibernate with the dual displays active and resume with just the laptop's screen, it may be that you will get no display (actually, the display will be full of useless vertical black and white lines). The only way to get out of this is to power cycle or remote ssh and reboot.
On other occasions, if the external screen was the main screen, you may end up having the laptop screen being ok but the Unity focus still be on the external screen (which you unplugged), thereby preventing you from doing anything useful with the desktop. You cannot even reboot since you cannot clock on anything. Again, the solution is to reboot or ssh remotely.
I am using both setups, one with Ultrabase at the office and one without at home.
My experience is different. With 11.04 it was a bit unstable. With 12.04, it works like a charm. (I never bothered with 11.10).
Try it.