No major problems with Permajet on an R2880, just need to make sure you print something regularly otherwise the heads tend to clog. Also be careful with the installation, the ink tubes can get nicked on the black plastic carrier you also install to support them. You'll get great results on their FB papers and Fotospeed Platinum Baryta.
I think it will partly depend on your printer.
For example, I use a Canon Pro9000 mk2 with German OCP inks and I refill the OEM carts......dead easy and my ink costs are about 10% that of using OEM carts.
I also have a R2880 using OEM carts and I am currently researching an alternative and will definitely go for refillables again. I tried CIS units in the past with a R1800....they worked ok but probably no cheaper than refillables. Also, I didn't really like the printer lid being open, the tubes and bottles everywhere but had my environment been different and I anticipated long print runs a CIS would be a stronger contender.
I have looked at several inks and cart suppliers...Marrutt inks seem ok for the R2880 but still thinking about some American made inks as well. Am even thinking of buying Epson 220ml carts and decanting the ink!!
If you are selling the prints it is sensible to only use longevity tested pigment inks. Permajet are for the printers that are covered. Lyson / Marrutt and Fotospeed - I think I recall seeing that they have been tested and certified.
I used one and when it worked it was excellent, but it was very problematic. Lots of time consuming babysitting the printer when I was doing huge runs.
Then when I started getting complaints from customers as to the quality I switched to using a pro lab.
Cost is only marginally higher, but no complaints and much less time consuming. Plus the pro lab prints look better anyway.
Based on my experience it probably still worth it for large runs of draft and stationary, but then its debatable because you can buy cartridges super cheap of the internet and for that sort of work colours and longetivity don't matter anyway.