The initial 3-stage build seemed to take forever (at least 3 hours, possibly more), but it's finally over. I'm running the testsuites now to check for any problems before I make the final install.
Also, I get the impression the testsuites take a rather long time, as well... Although, this all might be going faster if my computer wasn't older than dirt. I've got a 5-year-old Hewlitt-Packard running at 1.2Ghz on a Celeron with 256Mb of RAM. I'm pretty sure the latest computers would've gotten this all done *infinitely* faster.
Also, I'm not entirely sure of the exact list of prerequisites... I personally have every Cygwin package posted as of a couple weeks ago, but I know there are some basics that you *must* have to get a successful build, and there are also a few more to successfully run the testsuites (Which I highly recommend... We all know how Cygwin is. If there's a problem, you'll want to know ahead of time.).