Since you asked I like the overall pen but the shape of the barrels looks a little off to me especailly the bottom. It may be the photo or possibly you were going for a different shape.
On the lower barrell it seems to go down then back up kind of forming 3 mountains. If it was something you were doing on purpose I would guess that you would need to define the shapes more. On the top barrell it looks pretty good but you seem to come out of you curve to early so that it is pretty flat going down to the end cap.
I know all of this seems kind of picky and alot of this is totally subjective. I do not mean to sound negative since the overall pen does look nice. I really like the turquoise accent band that you added.