This can also let you expand the ground plane coverage; the yellow trace around the outside of the board is redundant with the ground plane.
There are also serious scientific discussions on the internet where right angles let high speed signals fly off easier and generate more emissions.
Unless you have somer reason for the board size, this board could be a lot narrower.
Your traces are all 0.1" apart, that can be tightened up.
No mounting holes? Why all the extra unused pins on P1?
I've ripped up 80x100cm boards all the time while working the placement, just keep clicking traces. Only takes a few seconds, there are less traces there then the connections made just to a 40 pin uC, let alone the rest of the board.