We use Polycom VVX311 and vvx411 works like a charm. Polycom VVX301s should work just fine. Make sure they are on the latest firmware.
The only thing I wish was polycom vars in the FusionPBX had a variable for setting the VLAN during provisioning, as we have clients that keep their phones on seperate VLAN and we have to manually program them for the correct VLAN.