The printheads are removable. Soak them in about ½ inch of hot water for fifteen minutes and then run the cleaning routine again.
I think the happiest day of my computing experience was when I got rid of my Canon 620 and got a HP 722. It is not worth the price of new printheads in my opinion. Print quality sucks by current standards and the ink cost was off the wall. It also gummed up if I went away and did not use it for a while.
Buy.com has an interesting deal going until the end of the month. Buy a HP 840 or 930 on the same receipt with a $48 E-Stamp starter kit and E-Stamp will rebate the full cost of the printer minus shipping. They will also give you $50 in free postage ($45 after their 10%). The 930 has the new RET III heads.
The deal:
http://www.us.buy.com/soft/product.asp?sku=20299878