I rooted my phone a little while ago and the process involved moving Linux utilities over and getting Android to run them. If that's the case, and the Transformer has already been rooted, wouldn't it be simple to just move GRUB over onto the TF and then be able to install Ubuntu, Debian, or MeeGo?
I know it's possible to "run" Debian or Ubuntu on Android devices, but it involves chroot and VNC, which basically runs Debian inside a VM (not really, but close enough). I'm talking about a full on install: GRUB with an option to boot the ARM version of Ubuntu that could even be on your MicroSD, and also an option to boot into Android.
Actually, I wonder why Asus doesn't ship it with the ability to install other OSes. It's not like anyone's really going to put Windows CE on it and the only other OSes I know of that support ARM are Linux, and even just a handful at that, and even out of those, MeeGo is really the only one I would want on a mobile device like a tablet. But still, even with that limited number of options, if they gave the option to dual boot into both Honeycomb and MeeGo? Ohhh......It would be sweet. It would be good for MeeGo, it would be good for Asus (providing optional functionality is always good), but it might be bad for Google. I don't really see people buying an Android tablet and then solely using Linux on it, but I guess it is something Google would have to worry about. But still, one can dream.