Having spent about 1 hour installing a clean copy of Snow Leopard and then Lion, followed by a seven hour SNAFU trying to get Vista > Win 7 upgrade to work on a Boot Camp partition, the misery of Windows is fresh in my mind.
In the Apple paradigm, I click on the Lion upgrade in the App Store (it knows I already purchased it). It installs, and we're done – no reboot. Just a video tutorial on new features.
In the Microsoft paradigm, I'm digging up DVD cases to manually type product codes that require me to needlessy recreate my upgrade path and make decisions about things like 32bit vs. 64bit. It's still installing Vista I type this, and the progress bar has been stuck at 75% for about an hour. The user experience: a scaled-up 640x480 installer that has been on the "Completing installation..." step for two hours.
It baffles me why anyone would affirmatively seek out this experience. As for the Intel "ultrabooks" – more vaporware from the 1990's-era PC industry. The "rest of us" have moved onward and upward.
EDIT: Windows installer just spit the DVD out and froze. Can't move the mouse. Time to start over! (I can almost hear them: Have you tried turning it on and off again?)
EDIT 2: If anyone is following this, attempt #2 failed the same way. This is hour 10 of trying to install Vista on a clean MacBook Pro 2010.
EDIT 3: Gave up and installed a VM through Fusion. Ironically, this is easier than a native Windows install.