I have custom firmware (3.90 M-33) on my slim PSP and a Cyclo DS for my DS.
I think homebrew is excellent. I can now play my PS1 games on my PSP using just my laptop burner, and games like Anti-Tetris and ‘Still Alive’ are hilarious. A lot of ‘homebrew games’ are rubbish because they are just pixel art floating around the screen. But 3D homebrew is great. I wonder if 3D homebrew is possible on the DS? I know it is on the PSP. I’d love to do a homebrew game from the art side of things, something like Halo DS or something :)