Refilling is really a money saver, I have been doing this for over 6 years. The key is buying the ink that is designed for the manufacturer's tanks/cartridges.
I purchased the pint bottles of ink from InkSite.Com in 2000, very nice company to deal with. Pint bottles are $27.00 + $5.85 shipping. The manufacturer's blend of ink for my Canon Printers.
Just bought hubby an inexpensive Canon printer and checked the model # with Inksite to see if the ink was compatible with what I have. Good news is that it was.
At the price of cartridges and tanks, it certainly pays especially if you use color printing a lot.
Don't believe the negative talk you hear about refilling.