I searched the Yahoo Epson4000 group using "MIS AND funnel" and got lots of hits on this topic. Some happy campers, some not so happy. Most of the complaints seem to derive from leaky carts, which MIS claims to have fixed. Colour issues seem moot, however we have no way of validating the authors' claims to "good colour".
Shewe's warnings are undoubtedly valid. He surely knows more about the 4800 and colour inkjet printing than I. You will be an early adopter.
On the other hand, there is the "fear, uncertainty and doubt" factor. Epson wants us to believe that their inks are magic. Based on some prints I see, they may well be right, but there's no doubt where Epson (printer division) make their money. And there's no doubt that ink jet ink, even in 220 ml carts, is one of the most costly liquids on the planet. HP uses the same business model. They state that their "imaging" ( ie consumables) division is their most profitable.
I believe that warantee issues will apply only if Epson can prove that the clone inks caused the damage in question. I'm Canadian. US laws may differ. You might want to wait until your warantee expires, as I intend to do.
However, according to MIS, with their "funnel fill" system, ink costs will drop by a factor of AT LEAST two, probably much more. The more you print, the more you save. If you're selling your prints, ink costs are irrelevant. If you're paying, they can be significant. Although they may not be solely in the fine art photography business, many service bureaus use bulk ink systems to avoid excessive ink costs.
My experiences with two Epson 1160s and an Epson 880 with MediaStreet clone (4 colour) inks and CISs over five years is nothing but positive in all respects. I have dozens of check-marks on my wall, each one signifying a near-zero-cost-to-me $85 cart change for my 1160s. I intend to experiment with clone inks in my 4800 so that I can use my printer guilt-free for what it was intended. Printing!