Concur on the spade bits. I started grinding them that way years ago, when I had to resharpen them, and have continued to do so.
I have to say, though, that the new "spade" bits from Bosch are terrific bits, at least for the remodeling that I've been doing a lot of lately. They have a screw-pitch center point, which requires a firm grip on the drill, but they smoke through the wood.