I'm one of those victims unable to upgrade from Apple Lion (10.7) to Mountain Lion (10.8). I'm working with a Mac Mini and have a dual-boot configuration. At first, the installer wouldn't let me upgrade at all because the RecoveryHD was missing. Through the help of a blog, I could download the Recovery installer from Apple (1.0 version) and then with a couple of terminal commands, I could recreate this in the current partition. In my setup, I moved my entire disk from what I had to a new SSD, so somewhere along the way the RecoveryHD got lost probably. Anyway, after that was created, the installer seems happy to prepare the install process and reboot. That's where the problems start. When the system reboots, I see the big "X" install process starting up and then it suddenly comes up with a dialog saying that mountain lion cannot be installed to the target location. That's when you find yourself in the purgatory between the installation process and nothing else, because not even EFI works at that point.

I've tried to slightly reduce the size of my "MacintoshHD" partition by 256MB, no luck. I've tried using the terminal to remove the EFI partition, because in my setup it shows as "Microsoft Basic" of some kind, which should actually be EFI. No luck due to "Resource busy".

In the end, at the top left in the Apple command, you can select the "disk" to use to restart the system. Select your regular, trustworthy MacintoshHD there and you're back into your regular EFI startup screen, where you can select either Apple or Ubuntu.

Some things are seriously wrong in the update process and I'm not sure I want to use the current software to do my updates. I'm going to try to write a report about this experience to see if Apple can redo some of this process or "auto-fix" some of the issues. I don't have anything valuable in the Ubuntu partitions that I care about (it's re-creatable in 1.5 hours or so), but the Apple philosophy is that things should just "work", and they don't without a proper indication of what failed.

So yeah... not a standard Apple as it's a dual-boot, but certainly using their hardware and some of the indications could be a bit more informative as to why things failed.