Two of my all time favourite pens are the Pilot Metropolitan and the TWSBI Eco. I think an Eco is the best TWSBI pen you can buy, and probably the best bang for your buck in any pen.
I loved everything about it, except for the black / white parts. TWSBI finally fixed that by releasing an clear version. And the result is an pen that looks almost as good as a 580. It looks cheaper, but not by much.
I love the Eco, while I’m not that fund of most of the other TWSBI pens because they are a little bit too expensive to make sense for me. Why buy that when a little bit more can get you a Vanishing Point or Lamy 2000?
Anyways. I’m loving my clear Eco.