I've been using a Raspberry Pi 3 for the past week, and have been pleasantly surprised by the performance. It's no speed demon, to be sure, but it's good enough for all my basic tasks. I wish there were a general "open computing" branch of the Raspberry Pi Foundation that would produce a $50-$100 "pro" version with more RAM and faster bus+peripherals.
The Raspberry Pi still relies on a closed-source blob running on a CPU core whose instruction set isn't publicly documented to even boot, but I suppose at least it's possible to reverse-engineer that unlike Intel ME.
Broadcom released a considerable amount regarding the Videocore IV a couple years ago. Nobody's finished writing an RTOS for it quite yet, but the ISA is now documented.
There are more "pro" oriented boards than the Pi series. ODROID, e.g. It indeed has faster I/O and better CPU. You lose out on the scale benefits from Pi.
Few if any of them have "enterprise" grade quality IMO. The ones that strive for this (HP Moonshot, e.g.) are significantly more expensive than $50-100.
Note that the topic at hand is binary blobs and trust and Pi and other ARM SoC fall short there.
