Buying ink for your home printer is always a huge pain. It is where the printer manufacturers make their money.
However after needing to buy ink for my Cannon Pixma MP620B I found InkForSale.net. I bought two cartridges on my first order, a black and a magenta. The black went in without a hitch, the magenta however would never take.
So I contacted InkForSale.net and they, slowly, replied and said they would send me a replacement. At this point, I also needed a Yellow cartridge. So I told them I would go ahead and order that and they can ship them together to save some money. Unfortunately when my package came it only had the Yellow cartridge in it. So I emailed them again and never got a reply, however the magenta cartridge did arrive and work as expected.
So three out of four cartridges worked fine, and they did replace the broken one.
So will I purchase from them again? You better believe it. The savings is well worth it. The big difference is that I will order more than I need and store the new ones.