Carl,
I am sympathetic with your observation that a three-pass CBC
using the basic DES code book is easier and faster than performing CBC
using an EDE codebook, given current DES chips, and maybe even some
software. With new software the latter approach is potentially
faster, though not by much, and the interface is cleaner, i.e., it
preserves the CBC interface, IV characteristics, etc.
However, the lingering question is whether the three-pass CBC
is as good as the EDE codebook CBC. History is littered with examples
of "more complex" crypto approaches. that turn out not to be as secure
as more straightforward approaches. I don't claim to be a
cryptographer, but I have some concerns that this may be yet another
case of simple is better.
Steve