I bought a case of this paper after reading this and other threads on Staples Sustainable Earth papers. I only have a Sustainable Earth notebook (spiral bound) and not their printing paper, so I have not been able to compare SE vs TreeFrog printing papers.
This paper is generally very nice to write on with most fountain pens. One Japanese medium nib (Platinum Cool medium) with Noodler's Black Swan in Australian Rose ink feathers and bleeds somehow (this ink usually behaves very nicely on most other papers). Noodler's Black is perfect, as always, and some other colored bulletproof inks that are prone to feathering behave nicely on this paper (Bad Green Gator, Fox Red, Luxury Blue). One of my favorite blue ink is Pilot Blue (plain Pilot/Namiki blue), which usually doesn't feather on most papers, but it does very small bit along the paper fiber, very much like the one shown in the closeup photo of Diamine Ochre in owenj OP. So this paper isn't perfect, but I like this paper because the paper and the surface is hard, and doesn't grab the nib like some other high quality laser paper does. In fact, some EF nibs that are too scratchy on some papers behave noticeably nicer on this paper (still feel enough feedback).
One side of the paper is smooth enough for pointed nibs like Gillott 303, Esterbrook 128, 358, Nikko G, etc. But this is not as smooth as vellum type paper, and fine nibs can get caught in the upstroke. 303 on this paper makes very fine hairline (but upstrokes have to be very slow and gentle). In fact slightly thicker Hunt 56 lays very fine hairline on this paper, compared to other laser papers. I use Kaimei "Sumi no hana" bottled sumi ink (the best bottled sumi I found so far) and this paper works better with the ink a bit on the thin side for better ink flow (that is, add a few drops of water if the line skips). Overall, I think TreeFrog paper is good enough for practice and daily notes, but not perfect. In comparison, Staples Sustainable Earth notebook paper has smoother surface and it is more enjoyable experience to write than this printing paper. This makes me curious if SE printing paper is any better for pointed nibs than TreeFrog... but I won't know unless some local member is willing to swap a ream or two with me.
I see no feathering with Kaimei "Sumi no hana" ink.
My daily note pen is Esterbrook 788, 805 or 988 (all slightly turned up nib, very smooth writers) and this paper is very good with these combinations. But the paper is smooth and durable enough to take telephone notes with a G or school pen.
I wouldn't write on the rough side with pointed nib pens. They are too rough and not very enjoyable experience. Fountain pens and turned up nibs are ok.
Edited by megaptera, 08 April 2016 - 18:37.