First of all, I have to say this game is definately one of my favorites, and people complaining that it wears you out playing are obviously playing it wrong.
Before you even start, go to practice mode and have a play around with the characters, learn some moves and get to learn some combos, otherwise you will have no chance against some of the harder levels of the game.
If you want a good fighting game to play with your mates on the weekend, buy tekken, its easily playable by anyone and if you want you can button bash and usually string together a lot of good moves.
Also, i definately wouldn't spend £40 on a game just to play as darth vader, go and buy battlefront 2 to get a lot more for your money star wars wise.
The character creator (or create-a-soul) is a very welcome addition, with thousands of combinations to make an existing fighter or a totally new one exactly how you want them, as all the different items of clothing/ armour have different qualities, and encourages you to experiment with either a high attack or defence, or just outlast the opposition with superior hp. Its also rather fun to make characters from other games or programmes, they usually come out quite good (The Hulk is a good one to start with)
As mentioned in the title, the online in Soul Calibur really is poor, i have not yet gone into a game where theres been less than half a second of lag, which doesn't sound very much, but makes a significant difference when fighting the host who will be lag free which is why i have given only 4 stars.
Overall definately a game i would recommend, but if you are wanting something to just pick up and play with no learning curve, buy pretty much any of the tekken series which are also great games, but spend a little time and effort on this and you will definately be rewarded.