The great thing about Arduino is the code. The open source code available for the Arduino is probably one of the bigger code libraries for any micro controller platform. The micro that runs the Arduino is kind of dated now but the all the available open source code keeps it from becoming obsolete. If you have a fairly common IC that communicates over RS232, I2C or SPI there’s a good chance someone out there has written a Arduino library for it. With the Arduino you can take a project that (from scratch) would have taken months of development work and put together a working circuit in a few hours.