All damascus steel isn't created equal. Basically "damascus" just denotes steel that has been created by layering and welding two or more different steels together.
Tim uses two excellent carbon tool steels in his pattern-welded blades, and his heat-treatments are excellent. His blades should perform as well or better than any carbon steel blade.
Damascus made from steel and a softer material, such as nickel, would likely have some issues.
I've tried double bevels a few times, and I think the technique works. The extra tape tips the blade up a tiny bit, so the finishing hone is cutting on a smaller area of the bevel. It allows the finishing hone to quickly remove all the coarser scratches from the cutting edge.
Another effect is that you wind up with a slightly more obtuse angle on the edge, which in theory makes it a bit sturdier.
I haven't found that it makes enough of a difference to make me do all my razors this way, but once in a while I'll do it just for fun. :)
Josh