I am a total noob here, so forgive me if my questions don't make sense or are just plain easy.  I noticed the newly supported Ubiquiti devices from the 11/20/2014 "newsflash."  

1-Can somebody please explain the advantage of the various supported models of Ubiquiti devices along with the M2, M5, and M9 designation? 

2-Do some have better range capabilities than others?

3-If I had a M5 device, will it communicate with the mesh network nodes that are M9's or M2's?

4-Can technician licensed individuals operate M2, M5, and M9's?  They seem to operate on different frequencies.

M2= 2.4GHz band

M5= 5.8GHz band

M9= 915MHz band

Just like a 2m radio can't talk to a 440 radio directly the same is true for mesh nodes, they only operate on the band they are designed for.

What model you choose will depend a lot on your area and their setup.

Inside of that each model has different TX Power and Antenna setups so you will want to look at that, some have antennas built in others require an add on antenna.  MIMO (two antenna ports) may be better than a non MIMO (single antenna like the bullet)

At the moment my area (San Diego County) is looking at 2.4 for all users, 5.8 for the backbone which is a somewhat controlled network, and M9 hasn't been looked at too much yet but may help on some unique sites.

As to what you can operate with, I believe all are acceptable for a Tech in the USA but suggest double checking the frequency allocation charts to be sure.

Eventually what we have planned here in Louisville is to have a couple "cell sites" that use all 3 bands linked together through a switch, though we have a few 900MHz repeaters so I will need to verify that the M9 would not interfere with the repeater operation.