I have been using Ebay bulk ink that costs about $20 in two different mx860s. Very good luck so far after three sets of bottles. IIRC he is called Devinshredder.
I have been using uni-kit inks for the past year. No clogging, no perceptible fading. I thought the colors looked great until I did a print profile (spyder3 print). Took a really closer look at the colors and they are off. I am using Costco's Kirkland paper.
So if you just do every day color stuff uni-kit is good and cheap.
If you are looking for good color accuracy Uni-kit is not the answer and I am still searching for a 3rd party ink.
The CIS that I bought on 2-1-10 was from devinshredder. The one I had was not recognized by my MX860. Returned it 2-17-10, still waiting to get one that works. Since then I've been using : http://cgi.ebay.com/15P-PGI-220-CLI...cmdZViewItemQQptZBI_Toner?hash=item5ad4fbca90
these work great. I can refill them and the printer keeps track of the ink in them just like the original cartridge.
Since, devinshredder was unable to get my CIS working he refunded 100% of my money. I will go to him again as soon as he gets one working with chips that I don't have to install.