I bought the Singh-Ray LB Warming Polarizer when it first came out. It is very subtle, adding a touch of warmth to the blues in shadows but not obvious overall. I haven't used it on wider than 24mm on a FF camera, so don't know if you 'll need the thin-ring version for your 16-35.
One nice thing about the LB is that it is "brighter" by 2/3rds stop than S-R's original polo filter.
It's been used in the eastern Sierra, southwest red rock country and Great Smoky Mountains.
No opinion on the neutral version, I haven't used it or seen it used yet.