Apparently the mp780 Canon uses carts that don't have chips in them and
the carts are REALLY cheap. These Canon machines are pretty highly
regarded so now I'm done with slow performance from the HP and
massively inflated ink prices.
I know this well, I own the mp760. It does have something that
resembles an ink counter, which I "believe" kicks in after the
reservoir side is empty, leaving 20% in the sponge.
http://www.steves-digicams.com/2005_reviews/canon_mp760_pg2.html. I
have never tried to run a cartridge empty so I can't speak about it
directly, but i'm told it will complain eventually if you don't replace
the cartridge after the "cartridge low" warning. Unlike you HP, you
"don't" want to run these dry as the head will cost you $80ish out of
warranty.
Ink is reasonable on the HPs, so long as you don't buy the cheepo model
or a low end all in one. Canons you do have to take the head into
account, which is officaly end of life after the 10th cartridge change,
but i've heard as high as 20. The head is covered under warranty, and
they don't drop like flies, but it's wise to mentally add $1.25 per
cartridge to fairly contrast a canon to an HP with the head on the
cartridge.
This being said, i'd probally still own HP if it wasn't for the ease of
refilling or CD printing. I find the canon AIOs to be a tad immature
in the software department. The springboard menu to make multi copies
from a scan goes through EZ photo print which only permits printing to
Canons. But as long as you already have software to use the scanner
part you should be perfectly happy.