This work's been a life-saver.
The procedure as described in ian's post worked for me.
The upgrade procedure for the BusPirate itself, however, could be clarified a bit more; but I'll admit it's a bit out of scope for this thread since the people that wanna play with this experimental functionality are most likely people that already re-flashed their stock v2-firmware-upon-delivery to the v4 firmware once already at least.
However, me, I bought a BusPirate and an OLS in one go; got them delivered at the same time and wanted to get cracking with the OLS; tough cookies because of boot-loader issues, the known story, by now. This meant that I got to face the learning-curve of dealing with the OLS and the BP and the multiple layers/levels of firmware upgrades of the PIC's, the Bootloaders of the PIC's and the Bitstream of the FPGA, all at once. Seems the only thing that didnt get a firmware upgrade so far has been the ftdi232rl
Take this post to mean : Woaah, excellent work guys! Programming with the BusPiratePicProgrammer worked for me given the steps (and .swf) as demonstrated and i'm mighty grateful for it.
Having said that: some of the tools are only available for Windows made things rather problematic for me.
Dragging my stuff to the office to play with it there on a loaner-PC seemed to be the only option. Kudo's for the multi-platform tools out there so far (pump-loader.pl, command-line BP-loader, etc); since i imagine a fair number of *nix-users are buying these products especially because of their open-source character and multi-platform tools, I imagine there's a fair number of people like me using these particular devices.