I played the game serveral hours yesteday for the 360 and here is what I can say:
1) So far it doesn't seem like Vadar is in the 360 version, but as others have said I wouldn't doubt it if they include him as part of a DLC package. (In fact when you start up the game it checks for downloadable content immediately).
2) The story mode is pretty weak. While it does continue the progression of each characters own story line it does so in a very . . . rushed fashion. It's 5 matches and you're done for each person and the 5 story matches don't vary much from one character to the next.
3) The matches on normal mode in story would be considered "VERY EASY" back in the soul calibur 1 days. Not very challenging at all.
4) Character customization feels somewhat strange as the whole process seems somewhat more convoluted than it should be. With that said, there is a much greater level of customization this time around than in Soul Calibur 3 including stat boosts from specific items, the physical build of your character, and a greater range of voices (to name a few improvements).
5) The Star Wars characters don't steal the show, which is nice. Although Yoda being in the intro movie felt so . . . out of place, the rest of the time you barely notice they are there.
6) The original cast play just as you would expect them to and while I don't really like some of the art direction with some of the characters (*nitpicking*) at the end of the day you feel right at home playing the game as the core formula hasn't changed drastically.
7) The inclusion of the instant finisher system is weird but not game breaking, thankfully. For those who don't know, this is a new system in the game which is supposed to prevent people from just blocking all the time. I never saw this as a problem before but whatever . . . anyway . . . there is a green orb next to each characters life.
If you keep blocking the orb changes colors slowly until it gets to red. Eventually your life bar will start to flash and if you keep blocking still the orb will just shatter and go black. At this point if your opponent hits ABKG the match instantly ends as they perform a finisher.
It's not an each thing to do (that is, get the orb to get to black) as you practically have to block from start to finish. Also when you land a strike your orb fills back up with color.
All in all its a somewhat weird but interesting addition to the game, though I don't see it playing a huge role in many matches.
9) The breakable armor system is neat although it's odd to be fighting against female characters and have their armor ridden pants literally blown away. (Doesn't work with all characters but it happened twice to me so far lol).
10) Of interesting note, the biggest change to the series gameplay is the "cancelation" system. It seems the most if not all cancels are handled differently this time around. Example, Xianghua's cancels are now performed by simply holding down the button combination of the original move: So say you are pressing down X + Y to perform an attack, if said attack has a "cancel" you simply continue to hold down X + Y and the move cancels. I think I like the new system of canceling but only because I sucked at doing them in previous titles lol.
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So, in the end, it's not the best in the series (Sorry, Soul Calibur for DC remains the best IMHO) but it certainly is a worthy addition to the franchise.
If you're a Soul Calibur fan I'd recommend getting it, especially with the inclusion of online play and soon-to-be (I hope) downloadable content.
Edit: Online Play Impressions and "Style Level" impressions
I didn't think Soul Calibur would play well online but I was wrong.
I'm around 27 matches in and so far it plays extremely well (for a fighter). Loading is near non-existent even with custom characters, which is quite a feat IMHO and anyone with a lag rating above 3, from a scale of 1-5, equates to a pretty damned good online match.
Finding opponents is quick and easy with Xbox Live (as most online matches are) and you can choose to either join a match (via quick play) or host your own (where you can choose the time limit and such for a match).
The ranked battles is really all I have touched upon and it's a pretty fair rating scale. You face off against opponents with a 3 match win scale and if you win you gain points. Bonus points are awarded if you do certain things in a match, ie: get a ring out, get some extra points). If you loose you loose points. If you gain 400 points you gain an online level. Your level is what ranks you on the leader boards but it also will show your win and loss record.
While there are some frustrating moments (like, say for example, a hit goes right through a player even though it should have connected due to lag), these moments are few and far between and it goes without saying that this is a TON of fun for any soul calibur fan.
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One thing I kind of noticed in story mode but certainly noticed in online play was the new inclusion of the "Skill Level" scale.
As you progress through the game with a certain character (online play, single player mode, etc) you will start to gain skill levels.
As far as I can tell, the skill level of your character is what gives you access to more complex movesets for said character.
Example: I played practice mode with Kilik to see how much they changed him and I noticed holding down and using his mid attack only did a 2-3 hit combo as opposed to his previous 3-4. Another words, the final part of the move was "missing".
I thought this was a simple change till I built up the skill level and then all of a sudden the move, and others, began to return.
I don't know quite how I feel about this, it doesn't seem hard to gain levels (it just kind of happens) but it is another intriguing game elements they have added to the franchise.