One click? Yes (mostly)
I think what mckinnej is getting at is if the Excel tile you want is way over off screen to the right, it's not one click to open the program. It's slide the scroll bar until you find the Excel tile.
But you can order your tiles any way you want. I move the most frequently used tiles on the far left so that they are always visible.
That being said, I think a better way to open programs from the Metro style screen is to type part of the name of the file.
For example, typing "exc" + Enter opens Excel. There is no dialog box necessary. Just type. I think that is awesome.
It works for everything provided you can spell.
Example: Typing "2012 Bu" + Enter opens my 2012 Budget Report.xls file.
If you don't press Enter you will see a list of possible file matches to pick from.
So yes to one click and there are other possibly more efficient ways too.
