I absolutely love this game! I played for so long, I honestly forgot that it's a demo. I actually kinda like that the day doesn't end until you want it to, but I also don't think a progressive day/night cycle would take away any enjoyment.
The only issue I can find is that you can't sell the fish you catch (I thought buying the fishing rod meant more income), lack of a cooking mechanic, and not enough storage. Upgrades for those would be nice, too.
I've also encountered a problem where, if the storage lets me add multiple of an item, it deletes them. So I lost all but one of some items, not knowing there's no stacking. Not devastating, though; it didn't slow me down much.
In short, this is amazingly done! Despite some missing mechanics, I've put a lot of play time into it already, and I'm so excited for the full game!