There has been many discussions about using the updated rulesets with DH, what the changes are, how a "conversion" might be handled, etc. If I were to start a new cmapaign, with new characters, I'd probably use one of the conversion made by Plushy or Snap_Dragon , but as we're years into out campaign, and nobody wanted to re-make their characters, this is what we ended up doing.
We use OW rules for almost everything, except Psychic Powers (a conversion was too much work). We've retained the Classes and their advance schemes from Dark Heresy, with some modifications to allow for new skills and talents.
As the characters hit Rank 9, we reject Ascension and let these characters instead use all branches of their career trees.
You can find my House rules here, and I welcome comments, suggestions and criticism.