To echo Thomas’s post about HP light ink usage, my C5150 definitely uses them:
I think I’m on my second light cyan and magenta, while I’m on my fourth regular cyan and magenta cartridges.
The one thing I have learned not to do is buy the six cartridge photo pack. While it looks a bunch cheaper (typically, $45 for six cartridges + 150 sheets of photo paper), the bundled cartridges have a much lower capacity than the singles – maybe 1/3 less. So you don’t really save anything, create more waste, and end up with far more photo paper than you can use.