Are those rewards cumulativ?

let's say for example the Warpsmith gift.

vogue69 said:

Those that make sense as being cumulativ probably are, such as flaming arm or warpsmith.

unaligned charaters will never gain "good" mutations, rather they have the chioce between Eye-Stalks and Intelligent Cysts?

I think mutations that give the same bonus like mark of tzeenech and warpsmith both give psy rating. You just take the higher of the 2 instead of adding them together. I believe it states that somewhere in the book regarding traits.

unaligned charaters will never gain "good" mutations

No, unaligned chars have the best chance at good mutations, about a double chance of getting what they want. Also, a char who is unaligned while selecting all corruptions, then converts to a god, will have the best set of gifts of the gods possible, most likely -- for a future Khornate, for instance its ludicrously awesome to have Illusion of Normalcy (ALWAYS!!! PERIOD!!! surprise as a Khorne follower, with that +30 or so bonus for surprise, which is insanely powerful with lightning attack and helps you close to melee), Nerveless Ennui (gotta love an additional ignoring of 1-9 points of critical damage per hit, although it seems the only way to experience pleasure is Ecstatic Oblivion used on you now), and of course, Dimensional Instability (go incorporeal for 1-9 rounds, while possibly being able to attack if your will is strong enough).

Other chars will want different things, of course -- if you want to look like a classic demon, you might want horns, wings, and a tail really bad, a female follower of Slaanesh might really want a chaos organ really bad, some PCs will want to become freakin' robots or daemonettes, etc. etc.

nethru said:

it says you can't have 2 marks of tzeentch. but it also declares the mutations as: the psyker gets the trait Psyrating (+2)

which I read as +2 to your current rating. Otherwise it would say Psyrating(2)