Will the Uno bootloader work in the Duemilanove?
So I researched it a bit, and there does not seem to be any problems with running the UNO bootloader on a Duemilanove board.

The biggest difference between the two seems to be the USB interface: 

USB interface

Duemilanove uses FTDI, UNO uses another microcontroller (ATmega8u2).

Since the USB to serial is transparent for me as an end user for the most parts, it doesn't really matter to me.

Leaner bootloader

The UNO bootloader is smaller than the duemilanove.