Ezekiel is the Dark Angels' best Psyker.  Unfortunately, he still is only mastery level 1, making him less effective than he should be.  He costs 50 more points than a normal librarian, so let's see what you get for that cost.

First, you get artificer armor, which provides Ezekiel with a lot more protection than it did in previous editions since it now protects him against many of the power weapons that he may encounter.  He also gains master-crafted weapons allowing him perhaps critical re-rolls, especially when it comes to his force sword.  Finally, the book of Salvation.  This by itself may make Ezekiel worth the points over a normal Librarian as it provides the Fearless special rule to all those near him.  With 6th edition, fearless has become a huge benefit with no down-side.

Compared to other Psykers in other armies, Ezekiel is still underwhelming.  He also has less protection than any of the other characters in Codex: Dark Angels as he does not have an invulnerable save, although adding him to a command squad could make up for this, especially considering his 2+ save and ability to attack at initiative with a force weapon.  I still would not pit him against many other top tier characters, but he will still perform quite well against most stock characters.  I also like the fact that Ezekiel now has the ability to generate powers from the 6th edition rulebook as many of these powers are much more effective than Ezekiel's stock powers.

Overall, Ezekiel is probably not going to make it in many of my lists (and the same can be said of Librarians in general).  Besides the other draw backs that he has, I am just unimpressed with psychic powers in general in this edition as now all units have a chance of negating powers and the psychic hood has been nerfed in my opinion.  But I might have uses for him from time to time.