In reply to Workflow for Designing Typefaces with Multiple Weights/Styles (Metrics, Kerning, Classes, etc.):
Commenting on a 2007 thread in 2012. Merry Christmas to all.
I only understood/could design a multi weight font from multiple masters when Glyphs app appeared. For me it was the holy grail (more like holy sh*t this can be done) kind of Eureka.
Once you understand and start to learn this process, it makes life as a type designer much easier :)
Also I recommend leafing through adobe's MM guide. Really important reading and good info over there.