I have a true 1080P on my 13.3" Vaio Z notebook which I run at the full 1920x1080. I would stick with that over this new MB screen. It's all about effective resolution when you are trying to get things done and that hasn't changed on the MB.
1440x900, same as the old "low res" screen.
I was going to say this, but I would say its slightly better because the "effective" pixels are sharper -- You could probably run a text editor with a smaller font and still feel comfortable.
The retina display is 2880 x 1800 resolution.
1440x900, or an optional 1680x1050.
where do you see the 1680x1050 option?
That's the old non-retina MBP. Edit: Apparently you can configure the retina MBP in scaled 1680 mode; I'm not sure how sharp that will be.