Animal Allegiance and Battle Fury is probably my favorite combo,
Become Ethereal is great to distract hits from a follower, and also useful for when you're about to go into werewolf form. You can also regenerate some some good health while ethereal. If you pick the lady stone, meditate on Feim with Paarthurnax and get 1 item of 50% health regen, you get +100% health regen while ethereal, which is pretty neat. With the amulet of talos and blessing of talos you can stay ethereal 67% of the time with the first word, 72% with the second and 75% with the last. With Morokei or Dragon Aspect you can stay Ethereal indefinitely. Great synergy with cloak spells and master level spells.
I think it's cool to mention that Stability and Fortify Alteration potions also effect Become Ethereal, you can get some truly ludicrous run-times with that, and could probably run it through even a completely natural Shout cooldown time.
Not to mention that Bloodskal Blade's beam attack won't break Ethereal (or Invisibility) as long as you don't hit anyone...So not only could you use this infinite BE, but also add a decent (ish) long ranged, multi-target attack that won't ever break BE, basically making you an immortal that can't be hurt at all.
Does it? AFAIK only Slow Time is affected.
Not as far as I'm aware. UESP makes no note of it like it does for Slow Time.
Yeah, I'm pretty sure Become Ethereal isn't affected.
Well I'll take your word for it, I could have sworn it did...But it could have just been me mixing the two up a little bit. Still even with Stability it can be a lot of fun