I bought the ECO immediately upon seeing it online. While you may purchase various colored bodies, I went straight for the demonstrator. I like demonstrators. The one looks pretty wicked when filled with Red Black ink.
This is a large writing instrument and may upset tiny hands. About the same size as my Parker DuoFold, this pen is quite a bit lighter. The stainless steel nib, which I bought in Extra Fine, lacks any flex and puts down a very solid, consistent line. It does feel a bit like scratching words onto a page, even with quality paper and ink. Perhaps a function of the EF nib, but I find most SS ones to be similar.
I like this pen. I think it will be wonderful for short personal notes and is so EF it may prove fun for sketching. The inflexible, scratchiness of the nib, however, does not inspire me to WRITE with it.
All in all, the TWSBI ECO is good, serviceable $31 fountain pen.
TWSBI ECO Fountain Pen Clear EF Nib via Amazon