Thanks, neuro! Somehow I knew you'd be the first to respond. ;-)
I tend to prefer warmer temperatures to my photos anyway, so the warming cast isn't an issue... and easily corrected in PP if it's too strong.
I was more concerned about localized color casting, evidenced by:http://ih1.redbubble.net/image.10891529.8309/flat,800x800,075,f.jpg
Which was referenced in an article discussing ND filters:http://www.redbubble.com/people/peterh111/journal/4421304-the-ultimate-guide-to-neutral-density-filters
As the article states about the above photo, the problem was encountered with an aperture smaller than f/22. While I don't plan on using such small apertures (diffraction), it still gave me pause in purchasing the B+W outright. Not to mention the author clearly favors the Hoya, which seemed to work well for him.
Either way, given that I won't have the necessary amount of time to appropriately test the filter before heading out to the East Coast, I wanted to get some opinions before sinking money -- and photography time -- into a filter I didn't have any experience with.
Thanks for the replies!
P.S. I wish you hadn't posted a photo using your 24mm TS... That lens is next on my wish list, but a ways off from the reality of owning in. </jealous>