I never played the first Dead Rising. I'm not really sure why. I have recently watched a Let's Play of it, though, so I've got a good grasp of what it was like. Playing Case Zero, if this is what the full game of Dead Rising 2 will be like, it'll be what a sequel should be, the same, but better.
I'll admit now, I apparently suck at this game, so take anything I say with that in mind.
First, I'll put some minds at ease, there's no bottleneck in Case Zero when you're bringing survivors back to the safe house. If they fixed it here, we can only hope they keep it fixed in the full game. Here, though, there's only 12 survivors (I've only rescued 5 so far, and you start with 1. And I've played through twice.), so you'll probably not have many people following you at any time. Survivors also seem to be pretty good at running through crowds of zombies without getting munched to death.
There's interactivity between this and the full sequel, in that the levels you gain carry over if you get DR2, but you cap out at level 5 here. I'm not 100% positive, but I think the level bonuses are semi-random. I got the backdrop when I hit level 2, died, and when I reloaded, I didn't get the backdrop until level 3. I think. If I'm right, there's probably pools of possible gains at each level, and whatever you don't get, increases probability of getting those bonuses the next level. Lemme tell you, I'm glad that the levels will carry over, because running around with only 4 inventory slots is brutal. Even the 1 additional slot I have now is immensely helpful.
Speaking of inventory, let's talk about what you'll be putting in that inventory. Healing items and weapons. As far as I know, the mixing of healing items in the blender is unchanged, though there's probably more items, and more effects. It feels like one of those "You better like experimenting and taking notes, or you're gonna need a strategy guide" bits, because despite the presence of a notebook/diary/whatever, there's no in-game notation of what you've found that I noticed. Weapons are a different story. While almost everything you pick up here can be used as a weapon, and most are at least decent enough to do in a pinch, as the saying goes, "If you want zombies killed right, you gotta make yourself an electric rake." ...Wait. Eh, whatever. YES! Electric rakes, spiked baseball bats, I.E.D.s, molotovs, and more are awaiting you as results of the combination mechanic. And unlike the potions system with health items, when you discover a combination for weapons, you get a card telling you what was used, and what it makes. There's two types of cards. Scratch cards, which merely give you the recipe, and combo cards, that give you a x2 PP (experience points) bonus, and a heavy attack, though I've yet to see any difference between normal and heavy. While the weapons differ in effectiveness, some of them are absolutely ridiculous for harvesting PP. The spiked baseball bat has two attacks, really: a wild swing that can take out a swath of zombies, and gives you 50 PP per zombie, or a shot to the head that gives 200 PP, but usually involves a quick cut of the camera to optimally show you burying it in their head. Then there's the electric rake I mentioned, where it's a one-hit zombie kill, and you can take out several with one poke, and you get 200 PP per zombie. There's another weapon that I actually did notice the heavy attack on, that will give 2,500 PP, and can occasionally take out another zombie nearby and give 200 PP (what the regular attack gives). The more PP a weapon dishes out though, the quicker it will degrade and break, so keep an eye out for the parts to make them. One complaint though is it seems rather arbitrary as to what you can carry in your inventory, and what you just carry in your hands. Yes, it tends to be larger objects, but you can keep a rake in your dimensional pockets, but as soon as you stick a battery on it, forget it. And the problem with items you just carry is if you get hit, you drop it and need to pick it up, or if you run across a quest item, you need to leave it behind.
I'm assuming that the mechanics between C0 and DR2 won't change much, which is why I went so in-depth. As a demo for DR2, it's sold me on it. I'd suggest getting DR2 when it hits whatever price point you feel comfortable with. But this isn't really a just a demo, it's a game in its own right, for 400 Microsoft points. Should you bother spending the points on it? Well, if you're getting DR2 on the 360, the early jump on level alone might make it worth it for you, but if you want to know if it's worth playing in its own right, carry on.
The game takes place in the Middle of Nowhere, Nevada. You get 12 in-game hours to complete your objectives. From my experience, that'll give you about two hours of play in one run-through. You'll probably play through more than once, though. There's probably at least 4 endings, since I got ending D on my first playthrough. The town isn't particularly big. About 3 streets, and some alleys. It can get rather confusing to navigate. A lot of doors are locked, but you'll still have a way in to the building. Some you find a key for, some you break a window, etc. Some of the event triggers aren't terribly clear, either. I think Capcom went out of their way to prevent sequence breaking, which is too bad, because some of the tasks are rather lengthy if you go through the proper order, and it's hard to tell when you open up new options for tasks. Again, this is where replaying really helps you out. Once you know when you can do critical tasks, you know when you're able to search out other tasks.
As a character, ol' What's'isName is okay. You can tell he's left a deep, lasting impression on me, eh? I have to say, his motivation seems better than Frank West's did, and he's got a better backstory for being able to do the stuff he can do. The few survivors I've found so far are also at least differentiated from each other a bit by personality and/or actions, rather than just being "the fat one." I only saw one psychopath (who actually nearly stonewalled me until I figured out the proper tactic for the fight), and he was okay, too, having the kind of attitude that you'll see in zombification-via-infection movies on occasion.
There's a more than a half-dozen weapon combinations that I've found just by combining obvious things, and there's probably a lot more you can make by being more methodical, and dozens of ready-to-use weapons laying about town in the form of wrenches, benches, footballs, and ad boards.
I mean, really, for 400 Microsoft points, if you're a completionist, you're likely to end up getting 5 or 6 hours of play out of this, maybe more. Especially more if you just like beating the crap out of zombies in various ways. If you liked Dead Rising, and want a little bit more like it, this is a good deal. If you're waiting anxiously for Dead Rising 2, this will whet your appetite and prepare you for the new mechanics, while giving you a leg up. If you just like killing zombies, this delivers in appropriately messy fashion. I can't really think of a reason to not get this game if you're at all interested.