I have had a 5100 for a while now, and I print somewhere around 3,000 prints a year on the machine. It has been a great printer for me, even though I have had some support issues related to a squeaky gear. The printer has some unique issues related to paper handling and the use of specific media types, but once you learn how to properly use the printer with 3rd party papers you are good to go. I love the ability to switch black inks on the fly, without an expensive swap. I also have an iPF 8100, and between the two of them they have been great for me. I don't notice any quality differences between them, and one can easily be used as a proofing printer for the other.
I would have considered a 4880, but I would need two units to prevent having to switch black inks. And the 3800 doesn't meet my needs from a paper handling standpoint. Both of the Epsons are great printers, but as I have learned so are the Canons.