So I got this Nord Sorcerer (Heavy Armor/Dagger Mage) that I've been building up for the Ebony Warrior. This guy's magicka pool is less than his Health 500:400 and he doesn't use spell reduction gear instead with enchantments geared towards survivability in outnumbered combat. As you may know Master and Expert Destruction can take it's toll on a caster's pool.
So what do I do when I often find myself in a casting bind? I throw down a Circle of Protection of course. I Whirlwind Sprint out of the fray cast a Circle and in less than a second I absorb the spell until my magicka is back to 100% and sprint back into battle.
I just discovered this trick this playthrough and some folks might already know about this, but I thought I'd share this with the folks that might not know.
Anyways, yeah Atronach Perk definitely has a long list of pros.