Years ago I managed to get hold of a few workprints. Apart from some mentioned here I got Predator 2. This one bascially had no credits and was pretty much the same as the released version. Darkman, which was identical to the released version except for some FX that weren't matted properly and probably had to be cleaned up a lot before release. And finally Starship Troopers, which had all the deleted scenes from the DVD still in it but a lot of unfinished FX work resulting in some "FX missing here" frames. Most of the workprints I've seen seem to be only slightly different to the finished versions. Would be interesting if preservations of ones with a lot of differences were done. Especially as a lot seem to be better than the final cuts.