I used replacement inks until they clogged up a print head and I had to throw out a printer (after wasting hours trying to clean the heads in various ways and get it working again).  To me the hours wasted and lost printer were not worth the savings in ink costs, and I moved back to using ink cartridges from the manufacturer.  Another consideration is print longevity: if you care about that, you're not sure you're getting the same longevity with replacement inks.

I didn't see anyone here mention the cleaning sheets that come with many Epson papers.  Twice I've had problems with paper feed with my Epxon R1800 (which I love), and each time the problem was resolved by using a cleaning sheet and running it through the printer several times.  Certainly worth trying before you give up and throw out the printer.