Pros: Awesome design; high ink capacity; screw to post; portable/pocketable; comes with wrench for disassembly and silicon grease
Cons: EF nib was dry for my taste
Admittedly, I am a fan of "modern-looking" pens. TWSBI definitely fits that description. Their packaging is widely considered "Apple-like" with its white base and clear lid with the pen suspended on clear stands. The pen itself is very unique, as most TWSBI pens are. It is essentially the tiny version of the TWSBI 540 and 580. The "Diamond" name assigned to the 540/580 also fits this pen, though from what I can tell they don't market this as the "TWSBI Diamond Mini."
I chose the EF nib for my Mini based on indications from others that the TWSBI nibs are around the same size as Lamy nibs. My Lamy F nib was VERY bold for a F, so I assumed the EF would be perfect. However, it wrote incredibly dry, even for an EF. I ran a brass sheet through the tines which didn't seem to help. I looked up a video on TWSBI's YouTube page which showed them squeezing the fins on the nib to widen the nib slit. I did that, and it got better, but was still not quite we enough for my taste. Next, I went over to Stephen Brown's YouTube page (SBREBrown) and watched his video on doing a waverly bend on a nib to make it write wetter. That did the trick. My boyfriend bought a TWSBI Mini with a F nib, and in comparison, my slightly waverly EF writes identical to his F. So ultimately, I think I just undershot the nib size for my taste.
Aside from those issues, the nib itself is buttery smooth. TWSBI's quality always impresses me, especially for the price. The piston filling mechanism is very nice, and allows for a very large ink capacity. What's great about TWSBI is they give you the tools you need to take your pen apart and do your own maintenance on it; underneath the Apple-esque packaging you'll find a TWSBI wrench and a tiny bottle of a fairly liquid-y silicon grease to grease up the piston ring. One other great feature is that the cap screws to post, unlike the 540/580. I normally don't post my pens, but with the mini the small size and the perfect balance of the pen posted lends itself to posting.
At $50 from Goulet, or $55 shipped from TWSBI's Amazon page, you can't afford not to grab this awesome pocket pen.