First of all, to correct some misconceptions: Canon printers do not drink ink unless you print low volumes and turn them on and off a lot between prints. Canon printers work well with non-Canon papers (e.g. Epson, Office Depot, Red River and Ilford) but badly with some Kodak and most HP papers.
I don't think that many owners use their S9000 for text printer - almost everybody will use them as dedicated photo printers and have another printer for text (as I do). I think that this is the reason that you haven't had any replies from S9000 owners about text printing.
Most 4 colour printers use dye based inks for colours and pigment ink for black, because pigment inks give the better text quality and longer life. All six colour photo printers (except the all pigment Epson 2200) use dye black, and therefore produce slightly worse text quality. They certainly all appear to be slower on text than 4 colour printers.
I would expect a Canon S9000 to give worse output than your Epson 640 on plain paper, labels, decals, etc. Consider getting a separate text printer when your Epson 640 dies.