Giving 4 stars for now, until we can test the heating feature of the unit later this winter.  Overall easy installation, and the unit rapidly cools down our 300 Sq. Ft. room.  It's runs quieter than a standard window mount A/C.  
Suggestions:
1.  Make certain that you have the collars that insert into the window slider unit angled properly so the collars do not lean on the window ledge.  If you don't do this their will be large gaps that will need insulation strips.  Note: even when the collars are angle properly you will have less than 1/4 inch gap on the end(s) of the window slider.  For a few dollars I bought a roll of thin strip insulation.  
2.  For obvious security purposes: Depending on window location, I recommend adding a window lock or a 1 X 2 inch board to place inside the window frame, depending if you have a standard double hung or casement window.  It would be great if the manufacturer at least added a short roll of strip insulation in the box.