Perks are what make you good at very
specific weapons through effects and abilties. (mace, dagger, sword, axe, fist, polearm, etc.)
Skills will probably make you good at
generic weapon categories. (skills such as 1h, 2h, ranged, possibly DW)
* There's perks. A backstab one for dagger and an armor ignoring one for blunt weapons is confirmed.
Daggers won't be useless like in Oblivion. The game is already looking better for weapons.