What a joke of a UI. This would never work for a desktop. Or at least for a person that needs to do actual work. You have a bunch of program tiles spread out everywhere and you're supposed to swipe around to get to them? It looks so cluttered and unnecessary. Cool navigation animation gets old real fast. Especially if you have to swipe around 8 panes of tiles to get to the program you want to start.
Live Tiles on WP7 are customizable. You can move the things you want/use the most front and center. I don't see it being any different than pinning your favorite applications to the taskbar or Start Menu in W7. Currently, when I need to use a program I don't use frequently I might have to scroll through a list of applications under "All Programs," so I don't think few swipes left or right is that much different.
Also, who's to say you can't begin to type out the name of the application you're looking for, and you'll get the matching item(s) on the screen, so you can then launch your program, like you currently can when you hit the Start Button, or just press the Windows Key and begin typing?
What we've seen so far is a video that was less than 5 minutes long, which hasn't gone into those sorts of details yet. I think it's a bit early to call it a joke and to say your programs are "spread out everywhere and you're supposed to swipe around to get to them."