The Pro Trinket 3V uses the Atmega328P chip, which is the same core chip in the Arduino UNO/Duemilanove/Mini/etc. However, it uses 3V logic and 12MHz clock which means it's good when you want a lower-power and lower-voltage setup. Pro Trinket is programmable using the Arduino IDE as you already set up, and 95% of Arduino projects will work out of the box!