I used to work Canon helpdesk. If you use compatable inks it can fook your printer and will invalidate your warrenty. The ink used by original manufacturers is often thinner than the cheaper options, so it blocks the printheads or damages other parts on the printer...

The way companies make their money is through the consumables, such as paper and cartridges, hence why printers, etc are quite cheap to buy in the first place!

Its up to you if you take the risk fooking your printer in the long run and it shouldn't cost too much to replace it if it does go wrong... Good luck