Cheap maybe, but if you really use Raspberry Pi a lot, you will find that Pi isn't that robust after all. I installed 20 of them two years ago, so far at least replaced 4 of them during the time. Can't comment on the recent models though.
I've been hosting http://www.pidramble.com/ on either a cluster of 5 Pi 2s (now 3s), or a single Pi when the cluster is on a road trip, since July last year.
The only downtime has been a result of power or Internet outages at home.
Anecdotal, but I now have some 36 different Raspberry Pis at my house, and while I've had two (cheap) MicroSD card failures, I haven't had an issue with any of the Pis themselves.
As long as you use quality 2A power supplies (1A for older Pis) and quality MicroSD cards, I don't think you should worry too much about reliability, and if you have a cluster with redundancy... That's kind of the point ;)
I had a lot of trouble with corrupt cards. Took care of it by keeping the file system in a USB stick, and using the SD card only for booting into the OS on the stick.
Basically, you format the drive for ext4, then copy the filesystem over with async. Then edit the cmdline.txt on the sdcard to point to root=/dev/sda2. It's rather more problematic if you have multiple usb drives, and there's a RPi forum message somewhere with a lot more details...
The Pi alternatives can have better specs at a even more attractive price point[0]. The Pi itself benefits from it's accessibility, if that is not required then pick one of those.
I got a pair of odriod's based on price/performance to act as NTP servers and have since removed them from service.
They both had the same MAC address on the NIC, which was not impressive and more importantly have about a .5% (consistent) outbound Ethernet error rate. Not ideal for a service utilizing UDP.
I also got an odroid XU4. As a replacement for a sheeva plug I was using as a home server. I was hoping to use the HDMI out into my TV and use it for browsing and streaming media. Unfortunately none of the distros produced by hardkernel fully work. There is always something broken in each distro. It's a complete pain. I don't know why they cant just produce a distro that has all of the hardware working at install time.
My Odroid X2 and another X3 don't have a proper MAC, it's stored in /etc/smsc95xx_mac_addr.
Now that I look, there are some receive errors reported by ifconfig on the X2, but I've never investigated them. The X3 is on a different network, and reports zero errors. (I don't know how much data either has transmitted, the counter will have wrapped as it is only 32 bit.)
But, I wouldn't recommend them to anyone not thoroughly familiar with Linux. Compared to the Raspberry Pi, there's not much documentation, and the kernel is pretty old.
