I got up and going with a 1284P @ 16MHz on a breadboard very recently. Successfully.
However, I am thinking I may want to go up to 20MHz, in order to keep up with some expanded abilities I am designing into a little robot. From browsing this forum, my impression is that a canned bootloader is not available, or that creating one is not as simple as just creating a new entry in the boards.txt file, a la the 16MHz Optiboot bootloader.
Is my thinking on this about right? There are vendors that have 1284P@20MHz robot controllers, but are a bit pricey. I seem to learn better if I can build something myself.
Thank you, Mark