Floodlight randomly, dimly lights even when lightswitch is off
It appears from the 45606 manual that this model is not designed for use with anything but incandescent loads:


  This dimmer switch is designed for use only with permanently installed
  incandescent lighting
  fixtures. Do not use it to control fluorescent lighting, transformer
  supplied lighting/appliances, motorized appliances or receptacles. The
  incandescent lighting controlled by this dimmer switch must not exceed
  a total of 500 watts.


And


  Minimum Load: 40W, incandescent lamps only.
  Maximum Load: 500W, incandescent lamps only.


From my understanding of these Z-Wave dimmers, the ones that are LED compatible utilize a neutral (white) wire. This model does not appear to have a neutral wire.



Dimmable LED Compatible Model

The GE 12724 (ZW3005) Z-Wave, In-Wall Smart Dimmer (Interchangeable Paddles) is listed as compatible with dimmable CFL and LED loads:


  UL Listed to work with dimmable LED &amp; CFLs 
  
  Screw Terminal installation; requires wiring connections for Line (Hot), Load,
  Neutral and Ground. Traveler wire required for multi pole installation
  
  Maximum Load: 600W, incandescent; 150W Dimmable CFL/LED