From the few video review/gameplays I watched.. Pretty much everyone agrees that if you look at it as "Survive" and drop the Metal Gear part... it's a decent game.
And also the reviewers.. were kinda pissed because Konami sent out codes for the game for reviews... and forgot to turn the servers on, which you need to save your character... oops.
I saw this last night and decided to grab it, got the code about 15 minutes after picking the game up. Since I've played about 10-15 minutes in the MG franchise (lifetime total) I don't have any connection that others do. I watched the gameplay and decided I liked the idea since I tend to like these types of games.
As for the character slot thing.. I assume that there will be people that will want a single player save slot, and an online save slot..