I personally never tried Copland, but my brother (who's a member of the ADC) did a few years back. I never saw it running because he meticulously respects the ADC agreement (he's definitely not the one upon which the rumour sites live !
), however he did tell me that it crashed so much System 7
seemed rock solid in comparison. (Notice that I did not write Mac OS 7.5
To be fair, the only developer version Apple ever seeded was in fact an early bird version meant for those who wished to write drivers for the beast. A few months afterwards, Gil Amelio, having seen the monstrous OS, decided that a billion for that thing was obviously money sent down the drain. Thus the Great Hunt for an Existing and Working OS was launched, which resulted in Apple buying NeXT. According to my brother, we can all be very thankful of Amelios decision. Not only because it saved Apple from bankruptcy, but because the resulting OS would have been condemned to be as unstable as the present Mac OS is (had Apple actually succeeded, because providing 100 % backwards compatibility was proving to be a truly daunting task).
In short, AdmiralAK, don't look for it as the Holy Grail. It could make an interesting download for historic reasons, however, provided you have a compatible machine...