It'd been a minute since I bought a new pen, and I've always wanted to try a vacuum fill pen so I finally pulled the trigger. The pen writes so well straight out of the box but that's always been my experience with TWSBI pens. The kon-peki ink is a nice beautiful blue that also seems to dry fairly quickly which is nice because I'm a lefty and it's impossible for me to write without making a mess lol.
During my last flight, I didn’t even keep the nib upright, and still didn’t have problems. I had multiple vacuum fill pens with me, including the VAC Mini and Pilot Custom 823, and none of them leaked.