After some tweaking, code improvements and remote code execution vulnerability fixes, I finally put the uploadprogress extension into PECL.
We are using the extension on the (soon to come) next update of local.ch, therefore it already got some real life testing and it seems to work pretty well.
And for all those wanting a dll for Windows, I won't try to make those, as I don't have a Windows development environment and even if I had, I have no clue about how those things are working on Windows :) But the sources are there, I'm sure someone will step up and provide patches.