As for CPL's, here is my 145mm CPL on the 17TS-E, which I often shift stitch to an 11mm fov.
The CPL, as NWPhil says, can be used very effectively for water and shinny services, I use mine for controlling glare and reflections on swimming pools, granite worktops and bathrooms.
I strongly suspect Fotodiox will have an 11-24 version of the Wonderpana out pretty quickly.
Darn, and I believed my 95mm filter was big....
Seems that the new 11-24 has an integrated hood, similar to other newer UWA lenses.
That alone is going to create issues adapting a filer system to it.
For sure I will wait to hear and see test results on this new lens - hopefully, it will at least be equal to Nikon's 14-24 f2.8.
I would not be surprised with the rumored price if the lens was a f2.8 - @ f/4 seems bit too much, but again, maybe it's really even better than Nikon's offering, and sharp right from f/4
The overall size and exterior looks seem fine for me, and if indeed supports a internal focusing design, then even better.
Maybe f/4 is the new f2.8, now that Canon is coming with higher MP cameras and what seems to be a more robust iso - time will tell.
Meanwhile, is very entertaining reading about all this in the main forums