I've got a couple of these (one M, one F), and I like them too. And they are definitely underappreciated.
I like them for a couple of reasons.
One, I have a nasty habit of chewing the backs of my pens - even my $$ Pelikan 600 has a few marks where I've forgotten precisely which pen I'm writing with when trying to work out a particularly tricky problem - so the all metal frame is particularly welcome. It's a very solid metal pens that resist chewing particularly well, yet despite that, it is a surprisingly light pen, at least compared to the metal Lamy 2000, or any of the Chinese metal barreled pens.
Secondly and maybe even more importantly, as several have mentioned, it is particularly resistant to drying out (beating even the Platinum Slip & Seal, I think).
Overall, I find them comfortable to write with not too short (like the mini), or too fat (a number TWSBI's other pens) for my relatively small hands, and while light for a metal pen, it has a weight, or perhaps more accurately a balance, that is a bit more pleasing to me than some of TWSBI's other offerings. It does have a pretty steep step-down to the section, and I was wary when I looked online, but I've never really noticed it. The section is also pleasingly satiny, which is great for grip.
I find it comfortable, and as usual the QC on the nibs is excellent. They may not be the best nibs in the world (Pelikan, for me), but they're consistently good.
Edited by RGH, 04 February 2020 - 22:43.