I really don't know how i feel about multiple protagonists, in LA Noire, i didn't being forced to just continue the story with a new character.
@victim, i'm not sure i like the one after the other idea, it may mean the character you liked is now gone, and you've been forced to move on and finish the game as a character you didn't like as much.
Perhaps, if you played through, got to say 3/4 of the way through, and there is a plot twist, but it is not all revealed, and we get a 2 MONTHS EARLIER, and we then play as another character, who ends then ends up, caught up in this same plot twist, which reveals a bit more of the plot, then we have another reversal of time, and we are a different character, and we get to this point again, and all is revealed, we now have to decide what to do, and how we will continue, who we will continue as, that way you choose who you will finish the story as.
And then after the story, mini missions (continuing on with drug trading, assassinations or whatever) and what not are tailored to that character, if you then play through again and choose someone else and see how the plot turns out that way, then you also get a few different mini missions (import/export lists, gang wars) etc...
It's an incentive to play through again, especially if you want to get 100%.