Demo's pretty fun, and the different unlockable flags are a nice touch. Highest dread I've got to was 4, though that was due to a lot of help from the enemy's friendly fire (though I guess would make sense for the brits and the french to take potshots at each other).
Not sure if I understood the dread mechanics right, seemed like it's kind of like an XP/level up system where higher dread = more enemies, but my dread bar was filling up randomly between dread level increases - not sure if it's a bug.
One thing I was missing a lot is some indicator of how damaged a ship is. Not necessarily HP bars or anything, just a couple of different models of ships at different states of disrepair - both for the enemies and yourself, so you have a vague understanding without having to look in the corner for your hull number. Also, repair kits are pretty binary at the moment (use them if your hull is under 70) and can't really do much when you catch on fire except to wait it out.