I imagine this will interest a very small crowd, but here's a year-old presentation to a Mac developers conference by Adobe's Troy Gaul on how Lightroom is coded. He shows the development environment they needed to build because they were using Lua rather than a more widely-used language. One thing (as well as a new term) that I picked up was that there was a “stretch goal” to produce a development tool for plug-in authors as (hot news folks) “it might get a little tedious” to use a text editor to write code. No sign of it yet, but here's hoping (after all, Ryan Giggs just hit a 5th).
Also read John Nack's post on Lightroom beating Aperture 6-1 - more for the comments from the crowd.