For the past few months, I've been compiling Blender using MSVC+scons, as some change(s) made broke the final linking with mingw+scons. Unfortunately, the change in question was causing an "internal error" in the linker, which was not a good sign.
Today, I finally got around to trying to install a new version of mingw with a newer version of gcc (version 4.x at last on Windows... half a decade later!). As I reported in the post linked above, last time I checked on the mingw site (over half a year ago), it was an utter shambles - hosting troubles every few days and little consistent clarity over the actual latest version available. That included no clear postings stating whether gcc 4.x was finally usable, available, and obtainable from where.
Well, it seems that since that over a month after that post, they finally figured out how to get their asses into gear, officially releasing a GUI installer for gcc 4.5 on Windows with a proper news announcement for it.
The installation procedure using this installer was smooth: after a short period of downloading, I had gcc 4.5 installed at last, with no hiccups along the way. Hallelujah! An example of working software (to counteract all the broken examples around).
So, with a new version of gcc installed, I set about compiling Blender with it again. What a relief it was seeing the nice and compact gcc compiler prints + warnings again after months of verbosity from msvc. For the first time in ages, I could actually see only the stuff that mattered, instead of being constantly bombarded by heaps of other repeated garbage which pushed the important stuff off screen.
Although I would like to have reported that I now have a working mingw build of 2.5 again, unfortunately I cannot say this. I'm still getting problems with the final linking step, so no working binaries yet. But at least the errors this time look like they can be worked around (new libraries or code tweaks should do the trick) compared to the former issue!