I find the whole idea of the Abyssal Crusade very interesting.
Clively makes a good point that as time flows differently in the warp it might have been 800 years, 8 hours or 8000 years.
I don't think the Marines would have abandoned the job, it's not what Marines do, those that turned renegade yeah granted, but the ones that left the Eye, I think they would have achieved some of their aims.
Actually, wow, they have fluffed it out a lot haven't they! I didn't know they had done this in the new Chaos codex, colour me excited.
From the article on Lexicanum it sounds like Clively is right, the Imperium got a sound pasting and seemed to have been amazingly counter productive 30 Chapters sent in only for the majority to turn rogue.
But damn, those Vorpal Swords sound badass.
Awwww, there's a Blood Lords warband now, that were mine guys

I wish they didn't name all 30 Chapters as well as my Chaos Warband had emerged from one of the Chapters that took part