It's a fun looking game for sure, and I suppose a cool way to make this type of gameplay more accessible for the casual folk. I'll definitely recommend it to my brother for his PS3, even though I know he won't like sandbox-type gameplay, just so I can have a go at no expense
but it'll do nothing that Gary's Mod hasn't already done.
To the less enthusiastic people in this thread: sandbox gameplay is something you either love or hate. Personally I've spent upwards of an entire non-stop day in Gary's Mod (HL2) with a friend, building partially destructible forts with fully working, wooden trebuchets/catapults to bomb each other from the other side of the map. Or building a sort of dry-dock, and carefully letting a destructible wooden ship down into the water, only to see it fall apart after 30 seconds of sailing. This sort of thing either grabs you, or leaves you with a desire for more structure and less fiddly 'work'.
I suppose if you're on either side it will be incredibly hard to realise what the appeal, or lack of appeal is all about. Let's all keep that in mind in this thread