the game is good, but it's not what i expected
well, the game definetly is good, but compared with its predecessors it's almost close to nothing. the graphics are a real improvement, not to mention the fact that you can control both kain and raziel in an alternative way (i.e. kain does his share of the story, then raziel, then kain and so on). the outcome of these events are that they meet face to face in battle. of course, this is obvious since raziel's arrogance is what destroys kain and the events take place in a full circle once again (if it were for kain, the battle wouldn't have taken place, janos audron wouldn't have been resurrected, thus he won't be posessed by the hylden). this is something that could have been avoided in the game and create another set of events (who knows, maybe another game. but it wasn't meant to be. sad really). although, if you played the other games (blood omen 1&2, soul reaver 1&2) and payed attention to the storyline, you would have noticed that, even if Defiance is the last game of the series, there is still a small frament of the story which is not presented in the game (nor in the other ones). if you play the game you notice that the end of it, is when kain defeats the elder god and returns to the citadel. now the part that is not presented is when kain takes the reaver back to avernus cathedral for his younger former self to find. last but not least, the storyline had much less events than the other games. that's what dissapointed me the most. most of the time you have to just beat stuff up. there's almost nothing logical for you to do (of course there's the health talisman, the telekinesis or TK rune and the arcane tome but these ones don't count anyway because they're thought to be so called optional quests).
characters:
the way characters move are an improvement as well. both kain and raziel are more flexible, they can do mid-air attacks, dodge attacks faster and not to mention that they even level up (now that's something you could really enjoy because it opens up a new set of combos for you to try, which are quite usefull). but with all this comes yet another dissapointment. the enemies are quite weak, which means you level up pretty fast (there are 5 levels for each of them) and if you really get the hang of the game (i mean if you enjoyed it and want to play it again) you notice that you can level up even faster (i.e. get all 5 levels at about 40% of the game or so. THAT'S NOT EVEN HALF THE GAME). most experienced players use the enemy as a dummy (i.e. throw him in the air, strike him twice, use the TK to pull the enemy towards yourself – this triggers a shield of TK which throws the enemy back into attack range. you repeat this until you get down on the ground again. and if you look at the bottom of the screen you notice that your reaver is already charged to its maximum. this way you level faster). this is kain's case. and he used only ONE enemy. for raziel is a bit difficult but it's pretty much the same thing. the TK is useless for raziel as well (in battle that is). of course, i'm talking about the TK you acquire when you defeat turel, your brother. unlike kain, raziel has to use both of his hands for TK. then he has to summon the reaver again. (the delay is quite annoying especially when you're not a beginner, and you're used with kain to use the TK in battle). but there's an advantage that raziel has over kain. he's more agile (not to mention that his combos look cooler). if you like the finesse and agile type (like raziel) rather than brute force (that's where kain comes in) he's your man.
things got different:
unlike blood omen 2, kain can't use all of his special powers when he wants to (some of them can't be used at all). he must have different markers on the ground in order to use them (bat flight and long jump). i suppose this is excusable since the events in BO2 take place after the ones in Defiance (even if the games didn't appear in that order).
raziel can use his reavers anytime he wants as long as he has them (i'm talking here about soul reaver 2, where he had to charge his reaver with the desired element once again after he shifted into the spectral realm). and there are a couple of new reavers for you to try as well.
i recommend buying this game. i would do it more for the storyline than the gameplay. but you'll enjoy it nonetheless.