I am not finding any specific info in the guide or uesp on this. But I can't quite figure out what is up with these. Looking at the perk list it mentions sweeping sideways attack on two-handed, but i can't seem to do one consistently using the old strafe right power swing..... What is really strange is I think I did one once just flubbing keys in panic....

Hold Attack key while moving performs different power attacks.

Well thanks but as I stated I am doing that and it doesn't seem to do anything but default to a standing power attack. I am wondering if it still does the 360 spin on sideways attacks?

No, it just does a big sideways swing. It definitely works - have you got the perk for it? It won't do anything without the perk.

yeah i have the perk, i am going to go try it again and see what happens, I could have sworn on one of my charaters I saw her do a spin while executing a PA though, not sure which kind of attack.

I know without a doubt that this is the intended method for performing a sideways power attack:

1) Hold either the left or right direction
2) Hold the attack button until you swing (don't let go).

If it's not working, I'd report it in bugs.

360 spin happens when you are dual wielding. hold both left and right mouse button.

To be honest I haven't checked how it looks in 3rd person, so it's possible that there's a spin. You definitely don't spin in 1st person though, thankfully.

Let me specify: I am talking about with either the two handed or one handed skills, but I can't recall if one hand even gets a sideways or backwards PA. Right now, I am concerned about my two handed sword wielder.