I do use a Canon BJC80 portable printer with USB cable on my iBook or iRDA on my Psion 5mx PDA. Both times for printing logbooks, routes, waypoints and weathermaps from internet.
It isn't that fast but enough for these situations. The BJC 80 has a very small footprint (30 cm x 15,7 cm x 5,7cm; 1.4 kg) but can print on DIN A4 paper and in color.
The new IP90 can accept Bluetooth as an option so you do need less cables. To use bluetooth you don't need to buy the expensive Canon Bluetooth USB stick, II do use a normal BT USB stick on my Canon Selphy CP710 photoprinter and it works great.
But I like the retractabel cabels (USB, Ethernet, mouse) very much as they don't use much space.
The IP90 is fast and great for photoprinting, it's some mm bigger than the BJC80.
Unfortunately the Litium Accu is optional with the BJC 80 it was standard!
The BJC 80 is still available on ebay.
(German link)
http://computer.kelkoo.de/b/a/ps_1010893/114901.html
or
(UK link)
http://computing.kelkoo.co.uk/b/a/sbs/11...53643.html
As for the HP portable printer I did find these always too big and the batteries were always optional if I remember correctly.
And I think Canon does have better MAC OS X support!