I strongly concur with this request. Source Code Pro is great.
In addition, some monospaced text on the Mac client (at least) is not truly monospaced. In particular, bold text is not spaced the same as non-bold text in Andale Mono. There are uses of monospacing beyond code, and even in code that is being presented to others, boldface is useful for emphasis. One must choose all-bold or no-bold.
It works in Courier (ugly and hard to read):
AAAiii
AAAiii
In this forum, there is no Andale Mono, so I can't illustrate the problem here.