We ordered two of the original ones for our office to play around with them, but only now, after 4½ years, I finally managed to find use for one as music player, after I decided I was too lazy to plug/unplug the speakers from my laptop.
Even if only 10% of them is in use (which would be a very very low estimate) then this amounts to an incredible success because you can afford to buy one, try something and forget about it without breaking the bank.
The raspberry pi is a game-changer because it gives you a full fledged computer for a very low amount of money, so low you can actually afford to buy one and let it gather dust in a drawer.
By the same token: I wonder how many Intel cpu's and the motherboards going with them of those that were ever sold are productive today. If you look at things this way the glass will always be half-full and you're not going to see the impact of the devices other than from an angle of waste.
But the better angle is to see what is done with them.
Yup. I currently have a Pi turning my TV on/off, because my Intel NUC doesn't support CEC. Is it necessary? Hell no. Would it have been simpler to buy one of Pulse-Eight's adapters? Of course. But I already had a Pi gathering dust, so why not just reuse that instead.
What it does is up to you, you are only limited by your imagination.
Most of this was done while we were on sabbatical. And we didn't have a lot of Internet access. But I'll try and compile my project into something presentable.
I use them more or less this way:
-One for the TV, it lets me watch things that the smart TV can't.
-Three controlling my 3d printers with octoprint.
-Two on each car for recording video with cameras and GPS info.
-Three or so for controlling DSLR cameras and motors for panoramas, 3D scanning and so on.
They are extremely convenient for making things for other people(job or family), like prototypes, as I don't need to interface(or spend time) with their computers, I can just give them a computer!! all without breaking the bank.
At my current office there is a pi behind every one of a bank of monitors hanging from the roof, at home I've got one doing file server in my cupboard, a non-tech buddy has one doing media centre duties, and so on.
Not a single one is in use.
And for running an emulator (SNES etc.) I will probably need another one with more power. Not sure what to do with the others right now.
I also ended up buying a 50 dollar ubuntu intel computer stick which was great, and replaced the raspberry pi for emulation.
I have a friend who has a 3d printer and tons of electrical engineering gear, who just loves his, and does tons of products with them.
[1] I remember when 'lite' was 1.44mb, not 2.5gb
Edit: Also, it ships with 100+ MiB worth of kernel drivers.
In my lab there are five of them that do a variety of tasks from adblock, media servers, file servers (and it's sister that does the offsite backups at a friends), ham radio stuff, etc.
I'm pretty excited about the new Pi Bakery software http://www.pibakery.org/ that makes it easy peasy to spin new ones up.
I think I've five (of different revisions), only one is in permanent use. Another is installed in a robot, and the rest are all collecting dust in a drawer or in a half-baked project bin.