I'm of the opinion that the +hp backgrounds are too powerful, moreso because they are active at *level 1*.
Worst case scenario: A rogue/ranger gaining +10 hp at the first level (starting with 20 Dex is not that uncommon for these classes) is not balanced. Any class that keys off Int or Dex as their primary attack stat not only gains significant AC bonuses, but also hitpoints. Granted, not every class can do this, but getting +hp off your primary stat that is already increasing:
1.) Your chance to hit
2.) Your damage
3.) Your AC
is a joke.
Conversely, not allowing them gimps Assault Swordmages, Tempest Fighters (and many fighters in general), Thaneborn Barbarians, Paladins and Avengers (and often Warlords) in to less flexible and potentially much poorer choices than others of their role.
And the Con-based classes can get all of it out of Con.