Coelocanth: Have to reinstall the game, unfortunately. There's no revert patch.
Aspenwood: Unfortunately, at least with the retail version, reinstalling doesn't help, as the stupid thing auto-updates immediately to 1.1; there's no way around it as far as I can tell. If you cancel out before verification you can't play as you're missing the day one 1.0 patch (thank you, online verification for a product I bought in store!), and if you go through said verification process or bypass it and patch the game manually you end up with 1.1. I don't see why they don't just put the day one 1.0 patch up for download.
All I know is I'm beyond fed up with this crap, and doubt I'll buy another game from CDP. There's been very little communication on their part, not to mention the whole going back on their "We'll never put DRM in a game" statements, and of course, all the problems they've created with this "patch."
And meanwhile, the pirates are playing without these problems.
I don't think it autoupdates to 1.1.
People keep saying that..but when I reinstalled it did a patch but it wasn't 1.1
I know this because the DLC didn't work, until I manually ran the 1.1 patch, which it did allow me to install. Had it already been up to date it would have said so.
Also, I've been playing my GOG copy pretty flawless since release..so not sure it's time to bash CDRP to hell and back.
Although I agree with the lack of communication part.