So, I finished playing Festival of Blood on Sunday night. This post may feature some spoilers for anyone who hasn't actually played the game yet; consider yourselves warned.
I'm... weirdly ambivalent about it. I loved Infamous and Infamous II. (It's hard to separate them entirely; they're two games, but basically a single storyline.) I posted some earlier thoughts on them, and on the Karma scale and the way that morality is conceived and applied within the game, here, here, and here. I love the way the storyline comes together; I love the game dynamics and the graphics and the voice acting, the little touches that really make the setting come alive. I love that it's possible to be extremely good or extremely evil, but it takes some effort either way; I love that part of trying to be Really Good involves Not Hurting Innocent Bystanders, and the way that means that you have to be really careful - especially with the really powerful powers.
Festival of Blood does away with a lot of that. It features the same protagonist, Cole MacGrath, and it uses the same engine and setting as Infamous II, so in a lot of ways has very much the same feel. Then... well...
First of all, it adds vampires. Now, in the original storyline (in the first two games), super-powers only appear after the explosion in Empire City, and they're connected to the item that caused the explosion: the Ray Sphere. This isn't a world in which some people have always had powers; it's a world in which suddenly, now, things that only happened in comic books and movies have suddenly intruded into real life. To maintain that sense of a more... realistic, plausible world, the powers aren't magic; they're basically psychic powers, brought out and radically enhanced by the device known as the Ray Sphere. In other words, the powers are A) a new thing; and B) amenable to scientific study, albeit of the Star Trek This-Sounds-Plausible-Enough-For-Suspension-Of-Disbelief variety. Except now, in this story, there are also vampires, and they've been around a lot longer than the sort of power brought out by the Ray Sphere.
Second of all, because this story is built around Cole being turned into a vampire and then trying to restore his humanity by slaying the vampire who turned him, the Karma meter is suddenly gone. There's no particular penalty for draining the blood of innocent bystanders; in fact, at a couple of points the game encourages it (and I think at one point requires it, though there might be a workaround that I didn't find). So this where I emphatically did not like the game: the Cole MacGrath that I'd just finished playing in Infamous II would never have killed civilians just to power his vampire-cloud-of-bats flying power while he was chasing a Bad Guy. He'd have found another way. But... that didn't seem to be an option here. (Evil-side Cole, from one of my previous games, would have cheerfully done it just to escape his creator's control - but, again, choices.)
So that was my first reaction: an Infamous game without the moral choices and moral consequences just doesn't feel like an Infamous game, and using the same character just felt wrong. What almost saved it, and what allowed me to play it all the way through instead of giving up in disgust, was the framing device: the whole thing is a story told by Cole's best friend, Zeke... to a woman that he's trying to pick up at a bar. That helped, because Zeke is probably some sort of Grand High Poobah of unreliable narrators. Except that in the very closing scene, we discover that the woman he's been talking to is a vampire herself, which means that enough of the story is probably true that all the my initial objections - This Doesn't Fit The Established Setting and This Is Out Of Character For Cole - that all of my disgruntled objections immediately came rushing back.
My second reaction was that it would have been very possible to create a story similar to Infamous, in which instead of receiving electricity-based superpowers, the main character had just become a vampire. Yes, the powers involved would be different, and the environmental hazards would change, but you could still do a fairly awesome story that way: something like Blood Omen: Legacy of Kain in a modern setting, with an awful lot of the same moral and social choices found in the other Infamous games.
This particular combination, though... It was kind of fun to play, but aesthetically it just felt wrong.
 Yes, I realize that my gaming tends to run anywhere from six months to four years behind whatever's current; and yes, I also realize that this makes my reviews essentially useless as reviews. That's... not the point. Not generally. Not much of it, anyway.
 ...before dawn arrives, because now we're dealing with magic and not bothering to rationalize how this makes any kind of sense...
 The powers could either be traditional horror/fantasy vampire milieu, or could plug directly in to the established world as a new variety of Conduit. Cole can already drain fallen enemies of their bio-electric energy, though it's considered an evil act; it's not like conduits can't have some vampiric tendencies already.