The real problems with refilled cartridges (that is what they are) can be twofold:
The first potential problem is if the cartridge has the print head as part of the cartridge. Since these not engineered to last indefinitely you do get lower print quality on them as they wear out. Usually you can get through a second usage without noticing it much, but they do deteriorate.
The second problem is that you never know what sort of quality to expect out of a refilled cartridge. Since the only reason they exist is price, it tends to be a low-bidder sort of market, and you get a lot of bad stuff out there. Sometimes it will be great, sometimes not. You just have to figure out how much risk you are going to take.
Oh... and if you are thinking of archiving your printouts (say, using the photos in an album to show you kids when they grow up), the re-fillers are never going to spend the money for colorfast inks. If that is not an issue, then you don't have to worry about it.