Is it true that in the One-Handed perks only Armsman affects daggers?
Is it true that enchantments that give boni on one-handed weapons do not work with daggers?

My understanding is that the "fortify one-handed" effect doesn't work for daggers no matter how you get it. Daggers should be affected by all perks except Hack and Slash (axes only) Bone Breaker (maces only) and Bladesman (swords only).

^This.

Enchantments don't work because of the backstab multiplier you can get for daggers via perks and items, both of which can easily put your backstab damage into the 5 figure zone.

I'm playing with PS3 but have the same problem, which some of us have talked about http://www.gamesas.com/topic/1271064-fortify-one-handed-enchant-and-daggers/ in this forum. Take a look if you like.