Trinket is supported on Linux, Mac OS or Windows!.

The bootloader does not affect RAM usage.

The bootloader on the Pro Trinket use 4KB of FLASH so the maximum sketch size is 28,672 bytes.

The USB connection is for uploading new code only. This is to keep the Pro Trinket small and inexpensive, you can use any FTDI cable to connect to the FTDI port for a Serial connection.

There is no Serial-to-USB chip onboard.

SoftwareSerial will not work on the 3V Pro Trinket without changes.

You cannot plug shields directly into the Pro Trinket.

The onboard 5V regulator can provide 150mA output, not 800mA out.

Pins #2 and #7 are not available (they are exclusively for USB).

Here's some things you may have to consider when adapting Arduino sketches:

So you'll be happy to hear that not only is Pro Trinket programmable using the Arduino IDE as you already set up, but 99% of Arduino projects will work out of the box! The Pro Trinket 5V uses the Atmega328P chip, which is the same core chip in the Arduino UNO/Duemilanove/Mini/etc.

Battery poack for adafruit trinket 5v