Noodler's Konrad Piston Fill Brush Pen?

[majolo]

Just noticed there's a Konrad brush pen available at Goldspot. I have a Pentel pocket brush pen that I use for sketching and I'd be interested if anyone can compare them.

 

How well does the piston fill work through the brush feed? Are there inks that work better or worse? The description says the brush tips are replaceable--any idea where replacements can be found?

 

Thanks for any info!