Rumors have been abound that heavy armor "makes attacking slower". I've even heard that it makes "power attacks slower".

Is there any truth to this- as far as I can tell it just slows my movement speed, but a perk can fix that... Making me wonder if light armor has any value for a warrior.

i dont think i noticed any slow down with my sword regarding my armor type. they just slows you down i think

No but, I do think you use more stamina when using weapons. Haven't comfirmed it though.

I wish Bethesda would confirm these things...

afaik heavy armor slows your movement speed only, aswell as increases fatigue spent while sprinting, be mindfull that there are some perks that increase swing speeds (in case ou are getting the perception from for exemple a dual weilding char).
havnt noticed any stamina change on power attacks in heavy armor, then again my non heavy armor chars dont use power attacks. (ps: normal swings dont use stamina)

heavy armor doesnt even impede on magic use.

Which begs the question: Why go anything except heavy armor? (unless you're role playing)

Seriously, light armor isn't really worth it.

It uses more stamina, but it doesn't slow you down.