For those contemplating between these two phones, here's a somewhat detailed comparison (by somewhat, I mean, I don't know if it's complete enough)
http://www.cellphone-reviews.co.uk/2010/01/motorola-droid-milestone-vs-nokia-n900.html
Summary:
Motorola Milestone
Pros:
-More Fluid UI
-Better Kinetic Scrolling
-Multitouch
-Longer Battery Life
Cons:
-Flat keyboard
-slower browser rendering
Nokia N900
Pros:
-Faster browser
-Better multimedia player
-Flash support on browser
-better keyboard
Cons:
-short battery life
-no portrait mode
-has some responsiveness issues (or do some items really require a double tap to open?!!)
IMO, Droid has the slight edge because of the overall user experience.

http://www.cellphone-reviews.co.uk/2010/01/motorola-droid-milestone-vs-nokia-n900.html
Summary:
Motorola Milestone
Pros:
-More Fluid UI
-Better Kinetic Scrolling
-Multitouch
-Longer Battery Life
Cons:
-Flat keyboard
-slower browser rendering
Nokia N900
Pros:
-Faster browser
-Better multimedia player
-Flash support on browser
-better keyboard
Cons:
-short battery life
-no portrait mode
-has some responsiveness issues (or do some items really require a double tap to open?!!)
IMO, Droid has the slight edge because of the overall user experience.