I've been watching quill18's England pre-release gameplay and the game looks pretty polished for beta - some CTD's and minor bugs, but from what's in the video I am confident that EU4 will have a release on par with CK2
I agree, between Quill18's playthrough (roughly 5 hours of gameplay, and counting) and Paradox' live gameplay vids on twitch, we had litteraly over 10 hours of gameplay. Hell, we don't even need a demo, we've seen so much already. The game is going to be fine. There will be some tweaking/bug fixing/balancing needed, this is inevitable with that sort of games, but they wouldn't have shown so much if they weren't confident.