(This is both my first post and first review)
I bought this pen a few weeks ago and have been using it quite a bit. This is my first modern flex pen so I unfortunately cannot compare with either Noodler's or FPR's models (I have three vintage flex pens though.) The pen I originally bought was a purpleheart and cedar wooden pen. Pierre (the make of the pens) had ran into some issues during production (from what I recall the cedar giving him trouble while he was finishing the wood,) so he gave me a choice of either a full refund or a pen made of another material. I told him my preference would be for an ebonite ripple pen.
The pen, as many of you I'm sure know, was built with input from members of this forum and was an attempt to build an "inexpensive, high performance, modern flex pen." I think Pierre has succeeded. The pen accomplishes it's lofty goal by using a flexible dip nib instead of a stainless steel or gold fountain pen nib. The downside is that they will eventually wear out and need to be replaced. Fortunately, these nibs seem quite long-lasting. I've been using the same nib for three weeks now and it's still performing great. Smooth, great hairlines, and no sign of corrosion yet. I do keep the pen stored up to not let the nib sit in ink while not in use. Replacement nibs are only a couple bucks though. Even less if purchased in bulk. For me, it's entirely worth it, even if I have to replace the nib each month.
The flow is superb. In roughly three weeks of fairly heavy use, I've only had a handful of instances of railroading. While I've only used this pen on either Rhodia or Clairefontaine (I use those papers exclusively), I don't believe this would work well on cheaper papers. However, that is to be expected with any flex pen.
The build quality is excellent and I think these pens are a steal at their current prices. I had read a few comments on Desiderata Pen Co.'s FB page saying that the pens seemed expensive which seemed ludicrous to me: it's a hand-turned pen with a hand-made feed and the asking price was well under 100USD. It's unreasonable to compare a hand-turned pen with an injection-molded pen.
I would highly recommend this pen to anyone who is familar with fountain pens and their upkeep and wants great flex. Because of the maintenance involved, it might not be a good recommendation for someone brand new, however.
For the record, I have no affiliation with Pierre, other than as a satisfied customer.
Here's a writing sample (please excuse my terrible handwriting)
The paper is Rhodia R 90gsm and the ink is Rohrer and Klinger Alt-Goldgrun for the Daedalus and the Wahl. Iroshizuku Yama-Budo for the Waterman and Morrison.