The TWSBI Diamond 580 got very popular in just a couple of years, and for very good reason. If you want a step up from a Lamy Safari or Pilot Metropolitan, and want to get the coolness and large ink capacity of a piston-filler for under 100$, a TWSBI pen would be pretty much your only option. Apart from the cracking issues on previous models (that are luckily promptly dealt with by TWSBI's customer service.), TWSBI makes some really neat pens, and the 580AL is one of the finest examples I've used so far!
I'm almost 100% sure that the 580 AL will be my next purchase. It have taken me ages to decide on anything. I knew I wanted a TWSBI pen, and I wanted to wait for them to do something about the design to limit the cracking issue.
I think, and hope that it have been solved with the 580 AL.