First of all its very very easy to use, and does its job well.
I only tested it through USB. No driver needed on my Windows 10. Documentation is easy to read.

I have a huge stock of fitting thermal paper, because i wantet one roll for my gameboy printer but had to buy a minimum of 20.
Similar to the Gameboy Printer it uses a moving printing head.

Things better done than the Gameboy Printer:
- very easy interface
- no batteries needed, power supply is 12-18V at 1A, internally converts down to 5V@2A also used to power the arduino
- can carry bigger paper rolls

Things not so good as the Gameboy Printer
- there is a gap between lines, very noticable on printing graphics, this is due to the linefeed mechanically connected to the printhead (see demo video)
- printing is black and white, the GB one can do a few shades of grey
- there is no knife edge to remove the paper

Problems i ran into
- Hypertermianl uses CR/LF this causes the text in the current line to be deleted
- Despite using only Power, Ground, RX and TX on the arduino, other ports are blocked
- it likes to tip over onto the paper roll, it is heavy
- the flow control on uart is to wait for an echo, this is an uncommon method
- there is no description of how to put the paper in

Things i see can be improved
- I would have prefered a form factor which is not a shiel/hat which has a screw hole in each corner (for feets or to mount it somewhere) and an FTDI Adapter compatible connector and not easy to tip over.
- Option for RS232 style hardware flow control
- better usage of the paper area