These were done with a Noodler's Creaper flex pen, the smallest one they make; I love the varied lines, and the fact that you can tweak the pens--literally take them apart to clean and service them yourself if you wish. (LOTS of good videos on that at http://gouletpens.com!)
I own 6 Creapers now, for use with different inks (and two I've played with replacing the factory nib with different nibs--one a Hero M-86 bent nib for calligraphy and one an antique gold Waterman--they just fit the small pen.)
At $14, I find these a fantastic bargain for a flexible-nib fountain pen!
I also own 2 Konrads and a big old Ahab--it's lovely but a bit large for my small hands. Holds a LOT of ink, though.
Here's my review on that pen: http://artistsjournalworkshop.blogspot.com/2011/12/noodlers-new-ahab-pen.html
These are nice writing pens, too--I use them almost exclusively to write letters and to work in my written journal/daybook, though I do own other pens. The nibs on mine are exceptionally smooth for a steel nib pen.
On the minus side, for some unknown reason ink DOES evaporate in the pens--something to do with the type of plastic-like material they're made from. Sometimes they need a kickstart, either spraying the nib with water or giving it a quick dip. Sometimes I need to tap them on the paper to get them started. And sometimes I just need to adjust the nib.
Of course any pen is sensitive to both the type of ink you're using and the paper you're working on. Some are a better "fit" than others.
What's been your experience?