After many deep and profound brain things inside my head, I've come to the conclusion that Dark Heresy 2nd Edition is just not worth investing in. For me Dark Heresy, the original, is still a good playable game which doesn't need to be brought in line with the other games.
Rogue Trader, Deathwatch, Black Crusade and Only War are meant to have stronger characters and powerful adversaries. Dark Heresy is for the average Joes of the Imperium. It isn't perfect. But most of what needs adding to or changing can easily be house ruled.
What the original offers:
(1) Characters who are not impressive when they start
(2) Plenty of homeworld options, which supplements and other games add to.
(3) Loads of skills and talents
(4) Loads of psychic powers
(5) Acolytes need to pay their way, rather than being exempt from having to spend money to aquire weapons, armour and gear.
(6) What may be lacking from the rulebook is well covered in supplements.
(7) Anything not covered in the rulebook and supplements can easily be gleaned from other games and their supplements.
So it may be an old, outdated dinosaur but it will likely stand the test of time long after 2nd Edition has lost it's "new toy" appeal.
That's what I think anyway.