I have eleven years of experience managing and teaching Arduino. I have done a lot of projects with it. In addition to the basic features of Arduino, i.e, monitoring of digital and analog sensors and control relays and motors, I also handled more advanced features such as:
1.) Ethernet and WiFi
2.) Sending information to the Cloud (Amazon/DynamoDB, IBM/Bluemix, Xively)
3.) GUI design using touch screens like Nextion and 4D Systems
4.) Handle devices using RF (xBee technology)
5.) MQTT
6.) Blynk
7.) Mesh networks with RF
8.) CAN and K-Line buses in cars and motorcycles
9.) App for Android using WiFi and Bluetooth to handle and represent the state of the devices.
10.) Java desktop applications to handle and represent the state of the devices.
11.) Storage data in Arduino and external EEPROM memory
12.) Connecting Raspberry and Arduinos using Client/Server technology
13.) Controlling external devices through Bluetooth and SMS messages
14.) Controlling external devices through SMS messages
Also, I have seven years of experience with Raspberry PI and ESP (01, 8266, 32) microprocessors. I have done too many projects with them.