I've decided to use Ardex K-15 to level the concrete slab in my
living room. If I just cover enough of the floor to make it level
the K-15 will range from around 1" thick to feather edge. But I'm
thinking I may get a better surface if I cover the entire slab
(13'x17') to some minimum thickness, say 1/4". But this stuff is
pretty pricey. I will be having a wood floor glued down after the
slab is leveled.

Any strong recommendations for or against feather-edging vs.
covering the entire surface in terms of durability?

Thanks,

Robert