Epson are a bunch of crooks, see www.epsonsettlement.com and also look up "epson" under the subheading "consumables" on wikipedia.com.
Epson cartridges are specifically designed to never empty completely of ink. Whenever you throw away an Epson cartridge, there will always be around 2mL of ink left in the cartridge (a full Epson cartridge holds around 13 mL of ink so your wastage is at least %15 of your ink). Epson printers print nice photos, but they are a complete rip off. Cost per photo with an Epson is at least 55 cents, with exception to their Picturemate printers which cost 29 cents per photo.
Individual ink cartridges are a good idea, Epson just isn't going about it right. With the older cartridges (the ones that had the yellow, magenta, and cyan all in one cartridge) if you ran out of one color you had to replace the entire cartridge. With individual cartridges you only have to replace the color that runs out. So ideally, individual cartridges are a great idea.
Some of HP's latest printers use an individual ink cartridge system. Unlike Epson, however, HP's uses a vacuum ink system that sucks out every last drop of ink from the cartridges. When it says you are out of ink, you are definately out of ink. Each color cartridge costs $10 and the larger black cartridge costs $18. If you need to purchase several cartridges at once, you can buy all 6 cartridges along with 150 4x6 sheets of photo paper in a combo pack for $36. I bought an HP printer, copier, scanner that uses this ink system and its great.
So in a nutshell, Epson printers are very expensive to operate. I recommend looking into a more friendly HP 6-cartridge ink system. I own the HP Photosmart C5180 if you would like to print, copy, and scan and the D7160 if you just want a printer.