I print less than 1% on matt stock with our SLD800. Results aren't bad, using my own profile with Permajet matt 230, but results aren't anywhere near as good as I can get on our Canon 8400. But when clients want inexpensive little matt prints, they seem happy enouigh.
The gloss and lustre papers, with home rolled profiles are really pretty good, though dark monochrome images are a challenge (ie with the Roman 16 low key monochome, I don't get the same neutrality that I do from the Canon). But still fine by drylab standards. If I get some down time, I'll run some new profiles, using the optimiser option in profiler, but ultimately, it's a six channel printer, with only one black, so I'm not expecting miracles. Epson, and Tetanal (who I bought the printer from) profiles were decidedly green in the monochrome images; Profiler profiles greatly improved things.
I run all my printing through the Epson print controller software, but bought Qimage for the profile charts. I'll have another look at the output with Qimage, if I get some down time next week.
B&H lists the Permajet matt 230 paper - the 800 (and I assume the 870) only take 65m (298') rolls - which is similar in appearance to Fuji matt bond, or Epson double weight matt paper, just a little thicker.
These little big printers are great fun - what are you looking to use it for?