Lets say i have a friend who joined the public beta, did a clean install on a seperate partition and wanted to contribute to refining yosemite with lots of feedback (about 60 reported errors with feedback assistant). Then Developer Preview 5 launched and he wanted to check if the errors were fixed. He installed the DP5 Delta Update Package (a friend of his got him a download link) and then continued giving feedback with the feedback assistent. Then yesterday he got hold of the DP6 delta update package and installed it. Everything is running smoothly so far but he is still experiencing bugs and graphical glitches here and there (its a beta, right?) and he wants to continue giving feedback with the Feedback Assistant. Is there something wrong with the way he did it? He is NOT a developer and aside from the obvious failure that he's not obligated for the developer previews, is there something technically important he is missing out by going "clean PB1 > DP5 delta update > DP6 delta update"? as i said, just hypothetically?