Critical Hits has posted their preview of Fallout 3. Highlights:
On the perspective:
[Todd Howard] began to explain the most obvious design choices as to why the game
is not in an isometric view but is primarily first person. The
reasoning is quite simple; they want to make the game feel like it is
real.
...
Everything that is visual about this game looks stunning in motion, so
much so to the point that it looked natural to be playing the game from
over-the-shoulder, and at one point Todd zoomed all the way out and up
to an isometric view while running and it still looked beautiful.