The Pico is designed to be easy to include in your own designs and builds. The .01" pins are easy to fit in to sockets, and castellated edges mean that unpinned Picos can easily be surface-mounted directly to a PCB. And to make it even easier, Espruino provided a part library for Eagle CAD that includes the Pico's footprint in several different configurations.
The Espruino Pico's fast response time has a lot of advantages. It allows for quick and easy debugging and is a great way to test your project before your big reveal. In addition, you can control the Espruino from almost anything - Windows, Mac OS, Linux, RasPi, Android, anything that can talk to a USB Serial port.
While the main advantage of the Espruino is its instant execution, it can also be used as a traditional board through a Web-based IDE hosted on your computer. The microcontroller also uses less power than Linux Boards (although its of course a lot less powerful as well) so will run longer on battery power, it has loads of IO pins, and it can be used as an IO board for PCs, Macs, or Rasp Pis without having to program it first. Simply take the Espruino out of its packaging and get started!