I'm a bit late to the Raspberry Pi party, but when the local electronics shop had a sale of model B+ I bought two on a whim. The new RPi 2 looks nicer, but B+ seems pretty nice too.
My Squeezebox recently broke down and I figured I might use one of the Raspis as the new livingroom music player. The sound quality might not be as good, but I thought I'd do a test and if I wasn't happy with it I would shell out for a better DAC.
The other Raspi is destined for our country house. I'm probably going to connect a Tellstick Duo and use some wireless thermometers and hygrometers around the house. I'm writing some simple scripts so that the Raspi can call home over 4G and report data now and then.
When I got the raspis I tested some different operating systems: Raspian (Debian-based Linux), Minibian (also Debian-based Linux - but much smaller standard image), RISCOS (minimal OS originally for the Archimedes, the first ARM computer), FreeBSD and Plan 9.
I'm running FreeBSD on most servers and would have gone that way on raspi as way, but FreeBSD on the raspi meant living without binary packages and compiling everything from source was veeeery sloooow. Had a look into cross compiling ports, but it seemed a hazzle. NanoBSD might be an option but I haven't tested it.
Plan 9 was fun, as usual, but not very practical. Haven't done anything on Plan 9 for a while. Tried a modern Plan 9 on my Thinkpad a few years ago and now on the raspi. A raspi seems to be a pretty good (and very cheap) Plan 9 terminal. Interesting to think back and compare the RPi against, say, the MIPS Magnum 3000 and the NeXTStation that Bell Labs once considered as low-end workstations they used as Plan 9 terminals.
The end user experience in Plan 9 hasn't changed much since I had Plan 9 on my workstation at work in the middle 1990s. Some things have changed behind the scenes, though, with a file server these days typically storing blocks of data indexed by their hash. The window system has changed a bit as well: rio, the 8 1/2 replacement, does graphics a bit faster.
Not much seems to happen on Plan 9 at Bell Labs. Most of the Plan 9 hackers seems to have left for Google and seems to work on the Go programming language. Plan 9 lived a long time at Coraid, though, embedded in their storage over Ethernet products, but Coraid seems to have shut down! Some development seems to happen over at 9front, a forked Plan 9.
It would be fun to do something with Plan 9 on the raspi, but I will probably just use some Linux distribution for the summer house raspi as well.