There are, at the time of writing, about 35 distributions which support the Raspberry Pi according to DistroWatch. This includes linux distributions, and a few BSD flavours too. Picking one should be easy, given what seems like a broad range of options. But... things are never what they seem. I have some very exacting requirements for a linux distribution I use.
The RPi B was the first single board computer I owned. It had been a while since I had played with a SBC. Sure, I had done some messing around with some eval boards and SoC reference boards as part of work, but nothing quite as sophisticated and finished as an RPi.
I am a huge fan of these credit-card sized devices. I love the idea that this tiny, solid-state bit of circuitry can outperform an 80's super-computer. I am totally enamoured with how easy tinkering and tweaking is. I am absolutely thrilled with how easily they are available. But most of all, I am thoroughly enraptured by the vast ocean of applications for this magnificent piece of hardware.