I first tried about 5 years ago with my HP. It didn't work well, refilling took 1/2 hour, and the print quality was crap, so I gave up.
I tried again with my new Canon i bought last year (Pixma ip5000). Works beautifully - I can't tell the difference. And it only takes about 5mins now that I know what I'm doing.
But: If I'm printing high-quality colour prints (photos), I prefer using proper Canon inks. I'm paying enough for the high-quality paper, so I don't want to screw it up with a bad lot of ink.
RoD