I did an upgrade installation of Windows 7 on my C111 starting with a fresh install from acer recovery cd's (Windows XP Tablet Edition), put on sp3 for XP, upgraded to Vista Business Edition and finally to Vista sp1 (Vista sp1 is necessary for an upgrade installation of Windows 7). I decided against a fresh installation of Windows 7 because I hoped I could force windows to use the all the rather old acer tools and drivers - and to my surprise it worked fine. (Some time ago I did try a fresh install of Vista and there were difficulties with installing wlan and bluetooth drivers, also automatic screen rotation didn't work then).
I enjoyed the new tablet input panel very much, the handwriting recognition works great and feels really smooth compared to Windows XP. The system seems to run just as fast as it does under Windows XP sp3 (I did upgrade the Acers hardware though with a newer harddrive and additional 1024 MB RAM).
There is however a big catch in it: Windows 7 beta does not provide a build in driver for the Intel 855gm graphics chipset, there is no compatible (wddm-)driver available from Intel and Windows 7 does not support the older xddm-driver model which was used under xp (and is still supported by Vista), so you are forced to stay with the standard vga driver. As a result there are two major drawbacks:
1) Screen rotation doesn't work: the standard vga driver doesn't support a screen resolution of 786x1024 (1024x768 does work fine though)
2) Hibernation will fail
I do not have much hope that there will be a solution for this issue, which really is a shame. Windows 7 would be a worthy upgrade otherwise.