An iRex DR1000 for those larger PDFs, a Kindle for fiction, and the iPod Touch because I had it anyway and it's ultra portable. Oh, and because I like gadgets
I've owned several 6" devices, but have eventually ended up selling them when I bought a new one as they ended up unused and in a drawer - not worth keeping them around. Each 6" reader has had some improvement on the former (Cybook -> Hanlin V3 -> Sony 505 -> Kindle 2 I'ntl. ) I don't think I should upgrade for a long while now though.... Been spending enough on new ereaders this year.