Huge fan of Dead Space here. Played all the games including the Severed DLC and even the original version of Extraction on the Wii (played it on the PS3 too!).
The video looks good, if you just have to put multiplayer on Dead Space co-op is the way to go. Thank God you guys at Visceral are doing co-op right and not forcing another player or a NPC with you at all times like Capcom does with RE nowadays.
That said my first play through will still be solo. But I'm definitely interested in trying co op, and I never even tried DS2 competitive mode. Maybe it was good but I never had the desire to try that out when I got the game, played DS2 3 times and at that time it was enough for me. I thought that competitive MP didn't add anything to the series. A few months later I decided to try it but couldn't find a single game to join.
If a fan who owns all the comics and animated movies based on DS and even has read one of the books fells like a new game mode is just not worth it you know it probably has some issues, or maybe that wasn't the way to go.
The only thing I'd like to add about DS3 is that I think not being able to play as Carver on single player is a huuuge missed opportunity.
Think of Resident Evil 2. 85% (probably more) of the content is still the same. There's very few areas exclusive for Claire or Leon. They're practically going to the same places. The major difference is item placing and the trench coat Tyrant chasing you on the second play through.
Imagine how great it would be if one run affected the other. Again RE2 is a great template for this.
If you don't have the budget to do a couple more different areas, just do different cut scenes, ending, expand the lore. Fans would still enjoy it.
A new perspective would go long ways to extend the replay value. He'll if you really want to milk it, make difficulty based achievements/trophies for both Isaac and Carver.
I really hope DS3 gets released digitally on the PSN. NFS Most Wanted and Medal of Honor all were available day 1. I don't live in the US, games are a lot more expensive here so I've began to buy a lot of stuff digitally.