As I use three R6220s at my home I can support the statement that it is very stable (as of 18.06.2).
Advantages of the R6220: cheap (depends on the country you are coming from), a lot of memory (128MB NAND/128MB RAM), dual core CPU, 2.4/5 GHz bands working reliable (if you don't run into the erase block issue), GBit Ethernet ports, AP/VLAN support, 4 SSIDs per band, Mesh support - and very important: a great tool (nmrpflash) to unbrick the device in case anything goes wrong
You will find a lot of current devices supported by OpenWrt but several cheap ones have network issues with one of the bands.
Disadvantages: The only significant one that I am aware of is the erase block issue. In case that you run into this issue you have different options:
- Wait for the patch to be tested and approved to fix the problem
- Use an image provided by one of the users
- Compile your own image using the work around patch with different memory addresses (called A and B versions) that I uploaded to GitHub (you can review the source code changes which are straight forward)
- Flash back the original firmware using nmrpflash and if you are in the European Union use the 14 days return policy to return the device with full refund.
Please keep in mind this is a low cost router (I bought it for 40 EUR) - don't compare it to an AVM Fritzbox for 200 EUR.