I have one, and I don't have a particular use for it.

The pros:

• It is as portable as they say. If you've seen a Fisher Space Pen, it's about that size. If you've seen a cigarette, it's a little shorter than that.
• Takes international short cartridges.
• The cap doesn't just post onto the back- it screws on, which is really secure and makes writing with it feel similar to a pencil.
• I have the black, but those fireblues do look nice!
• The nib writes better than my Ice Sport. (For now, anyway.)

So why don't I use this a lot? Well...

• It's tiny. I am honestly worried that I'm going to leave it in my pocket if I use it as an EDC. The pen feels pretty sturdy, and as long as it's capped, it probably won't be harmed in the laundry, but I'd be worried about the laundry.
• It can pretty much ONLY take an international short cartridge. Kaweco's own (mediocre) squeeze converter doesn't quite fit into it. I know I can use a syringe, but if I'm going to use a syringe, I want something like a Pilot-sized cartridge to work with.
• The cap screws on. This is something that, weirdly, ONLY bothers me about the Liliput. I guess I keep thinking about it like a fountainy Fisher, so I want a little more convenience than having to unscrew the cap every time I pull it out to use it. If it were a larger and flashier design, I wouldn't mind showing it off for a few seconds while I uncap, but for something so small and minimalist, I want to get right to writing.
• Last and definitely least, they misspelled "Lilliput". (Not in German, fine. It still bugs me.)

Anyway, those are my thoughts on the first >$15 fountain pen I ever bought. I don't know your writing preferences, or intended use for this pen, but I hope it gives you a little more information for making your choice.