The Koloro isn't a small pen by any means, but it manages to feel smaller in my hand that it looks. It's really comfortable when writing, and I've been very happy with how it feels over longer writing sessions. Just remember to unscrew the back knob a few turns to allow the ink to flow freely to the nib!
While it might seem like a nuisance to remember to open and shut the valve (the knob on the back of the pen) every time you want to use it, this is really convenient if you plan on traveling with the pen or if you know it will get tossed around a lot in a bag. The valve ensure that no additional ink makes it to the nib from the reservoir. Sure, there might be some ink splatter from whatever was left in the nib and feed section, but that's a finite supply. While it's not something many of us are considering lately, this makes air travel convenient as well. With a sealed ink reservoir, you're mostly insured against surprise ink burps that go along with the dramatic change in air pressure accompanied with air travel.