So in most ways that count, Ubuntu is already there, doing this, and it stinks. The basic OS is great, it is the UI that has problems. Ok, the "unity" interface isn't bad on my Asus eee PC 901. But on my desktop, it is less than satisfactory. I've got everything backed up, and an old test system running Mepis Linux (with KDE 4.5) and I'm about ready to switch my main desktop over to Mepis - the unity thing is that bad.
I wish MS luck - it is a modest technological challenge, but a huge human-factors challenge. Win 7 isn't too bad (just not my everyday OS). Hope they don't blow it with 8. But then, lately they've been running about every other major release toggling between good and terrible so I'm not holding my breath.
IMHO, the UI/graphics (and drivers) has always been one of the biggest shortcomings of Linux compared to Windows.