The highlights for me were probably the excerpts from the album, where they single out a lot of the little sections that were buried in the mix so you can finally hear what's going on properly. Might spoil the mystery for some, but for me having listened to that album inside out in my teens it's a nice look behind the curtain.
The early versions of songs they put out later are all good, and it's cool to hear them in more conventional rock song arrangements, but I wouldn't say are necessarily better than the final versions.
The demo of Let Down is great and shows that Thom pretty much had the whole arrangement worked out from the beginning. In fact the demos seem to suggest Thom writes more of the instrumental parts than I thought.
Also: Fitter Happier outtakes! Because who hasn't been crying out for those all these long years.
Apparently if you play the cassette in a ZX Spectrum, you get this: