Finallly got a chance to try KCSB last night alongside Booker's. I think dbk's notes are very good, especially with regard to Booker's and Baker's.
To echo what Gary and maybe some others said about KCSB: wow, it's all Beam. I don't mind the Beam funk like some do but I have to say I was surprised because this bottle at least is a fair departure from regular Knob in that respect. I think it was Parkersback who compared it to Beam Black at barrel strength and I can't disagree. Big flavors, pleasantly drying, unfortunately a little hot to drink neat but takes water and ice well. All in all a solid pour. And the price I paid is about equivalent to what I would normally pay for regular KC so I have zero regret on this one. Of course as an SB I'm sure the next bottle could be significantly different.
The Booker's, on the other hand, was superb. Easily drinkable neat even at 128 proof and change. Without writing a book I would say it reminded me of Baker's on steroids, with a little bit more depth and less peanut brittle, and a lot more fresh ground pepper. Wonderful stuff.