This will be a combination of a few things.
I bought my first Pi to play with. It now does mail for our home domain, DNS and a nice gui for the dabble into crypto currency.
I bought a nice combo that had a B+ board, power supply, case, heatsinks and on top of that a wireless dongle as I want it to run in the garage which has no cabling.
Unpacked it and put it in it's case and put the heatsinks on. Easy. Plugged into the TV and booted NOOBs. Told it to install raspian and it was away. All nice and easy.
Raspian boots up with LXDE but you can, in theory, install just about anything. Set up the wifi network and a few test reboots all looked good. I played with overclocking but it just made it less stable. We'll revisit that one.
Things to do on a new RPi I now know: firmware update (sudo rpi-update) and full dist upgrade(sudo apt-get dist-upgrade) of raspian. Both seemed to help stability as I had some USB issues to start with. Go through the raspi-config settings carefully and go to advanced update rapi-config before anything else. I've dropped the GPU memory to 16MB as it'll barely ever use the display. I had to turn off overscan as well to see the whole desktop. Seems odd that's on by default.
I have a mail server running postfix, dovecot and roundcube. All these just installed on the RPi and worked. Copied the config files from the old server and merged them. Copy certs from the old server to RPi.
The next step was to test a Gridseed (scrypt hasher) and it picked it up fine. Install a system named minera (http://getminera.com) which can be a full SD image or install on a running system.
The surprising thing is the RPi just keeps taking this. It seems to have more than enough grunt to handle all this. It didn't do so well when I tried a minecraft server as well. Might need another one for that :-)
So it sits in the garage with 6 gridseeds hashing away (it'll never make money but it's fun) and doing DNS for the home network and our mail server all over a wireless link. Seems plenty stable. I like it a lot! The idea was to stop leaving a full computer on 24/7 when something tiny and way less power hungry will do the job. So that's my bit to saving the environment :-)
My list of gripes are small and not really RPi related. The Gridseeds won't do SHA256d on the Pi, I have to go to a special windows build to do that but looking at it the gridseeds should be restricted to scrypt. They use 6 to 8 watts (4 apparently if you chop the fan) each and hash about as much as a reasonable graphics card (360 to 390 kH/s currently similar to R9 270). If you so SHA256d they use 5 or 10 times as much power.