I saw on this forum someone ask a question regarding nodes that didn't see each other.  The problem was resolved by changing back the SSIDs so they match (I'm assuming they were both running the same version of the firmware).

I notice that when installing different firmware versions on a node that the SSID changes. If the SSIDs are changed so that they match on 2 nodes running different versions of the firmware, will the nodes mesh and function normally? i.e. are nodes of different versions of firmware intended to function together if given the same SSID?

In 3.0.0 beta we are changing our version numbering scheme to make this easier for everyone.

The -v1,-v2,-v3 you are in the default SSID is the protocol version, nodes need to speak the same protocol version to be compatible.

Just renaming the SSID won't work, and will just cause confusion.  To date we didn't do a good job making it easy to know what versions are compatible.

Starting with 3.0.0 the version scheme will be that the first digit is the protocol version. This means 3.anything will talk to any other 3.anything.