The IR sensor only requires one digital input pin. On a Trinket, this leaves you 4 pins for other functions, on the Gemma, two pins. This gives you maximum flexibility for using an IR signal to trigger other devices like different Neopixel effects. See the Adafruit NeoPixel Überguide on how to connect Neopixels.
An IR sensor makes an inexpensive, compact (and nearly magical) input device to trigger actions in any project.