On the latest forge (.448 as of this writing) I find that the above procedure doesn't work. Now this might be me, since there is no "setup.bat" (I'm on FreeBSD here) and instead I ran "sh install.sh". Also step 5 is ambiguous to me as I don't know exactly where to copy the source into, so I copied it into "src/minecraft" relative to the mcp directory.
What happened was odd. The "common" tab in the eclipse project explorer had nothing in it and all the code had a lot of import errors.
I'd appreciate any assistance if anyone knows what's going on here. Thanks in advance.