Trumphy,
I'll take the first leap [Linked Image]...

I like Toroids. They "Hold" their fields much better than their Laminated "E" Core & bobbin counterparts (the magnetic field interaction is greatly reduced with Toroids - like when 2 or more are mounted close together).

They are used in Switch Mode Power Supplies (SMPS) for all Inductive elements (other than the AC Line filter - it's Inductor section is one of those "Back-to-Back zero sequencing coil arrays).

Toroids also used in Electronic High Hz Fluorescent Lighting Ballasts. The Controlled Reactors are tapped toroids.

TVSS w/ Line filters also incorporate Toroid wound Inductors.

I use Toroid wound air core Inductors in Audio system crossover networks (Passive Filtering of Speakers).
Either Toroids, or Perfect Layer stacks (also air core).

The major pain as far as Toroids go is how hard they are to wind yourself!!! My Brother-In-Law brought home a Toroid winding machine, so maybe I could use it for awhile.

Standard Core/Coil setups are relatively simple, compared to hand winding Toroids!

Oh, the largest Power Toroid Transformer I have seen so far must have been in the 5 KVA range. It was an Isolated Type setup, with 2 wire primary and a center tapped secondary.
I figure it was 5 KVA form it's physical size:
Apx. 6" Diameter ring with maybe #12 or #11 windings.

My Practical Transformer Design Handbook briefly covers the design data of toroids.

Scott35

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!