We have a winter knight in our game.  The Winter Knight Aspect gets compelled like any other (ie can be bought off) but the debt he's racked up gets used and not only doesn't net him Fate Points but also cannot be bought off.

Example - Mab wants him to muck about in the White Court's business and his Winter Knight Aspect is compelled.  He really, really doesn't want to and buys off the Compel.  Having him do this is something Mab really, really needs.  So she calls in some of the debt he's earned for the Winter Court aiding his magic.  This Compel cannot be bought off nor does it earn him a Fate Point.  So he's doing it anyway, because Mab owns him.

Dude.  The best way I've found to explain Aspects to D&D gamers is "Aspects are like your D&D character class".

Your character has the aspect "Barbarian".  He can spend a FP and get bonuses for doing things barbarians do.  He gets FP when his Barbarian...ness makes life hard for him.  When he can't read the warning sign on the rickety bridge.  When he's expected to be civilized.  When people won't sell items to him because he's a filthy barbarian.

I've done the same.  It helps immensely to put things in terms the players can easily grasp.  FATE, like ORE isn't a difficult system but it is one with lots of little fiddly bits and depth.  We had the bonus of moving to DFRPG after a True Blood game using the Smallville system so the players were already kind of used to abstract things.

What I do with any new game is gradually introduce new rules.  Do a quick adventure with the basics, Aspects, Fate Points, Stress Tracks, die rolling and then the next adventure add in something else and then something else etc.  Maybe even do a one shot D&D-esque game using the FATE system (I'd suggest even converting the essence of their characters over) so there's enough familiarity the players don't get overwhelmed.

Both of those characters are PCs?
I missed that before, I guess.
Did both of them get fate points (/reduced debt)?

WCV got Fate, Winter Knight got reduced debt, I got to pull two PCs kicking and screaming into the machinations between the White Court and the Winter Fae.  They were both trying their best to stay out of it, but now they have a kid on the way that both sides want....well its pretty easy to make things all kinds of messy:)

If the players don't already know that she is without a doubt Kedar... One way to do it would be to make him a separate NPC with similar  but slightly different stats/powers/aspects/etc and let them go about doing things like tracking down her second in command and dealing with his wing of te organization with the intent of weakening her power base then tweak her a bit based on how they dealt with him.  You could even reveal the two to be mtes or somethinglike the Eebs were to add an extra aspect that gives her a leg up against the PC's depending onn how they deal with him if you do that.  Another possibility if you go that way is maybe he makes the same sort of security mistakes as daddy Raith but her take on security is more like Laura's

The NPC hasn't been introduced yet.  The PCs have stumbled upon the beginnings of the plot and at the end of last session began seeing if they could track things down to a source.  My plan is to have the source be an expendable underling so that Kedar can be on the scene as another "hero" (and I use that term loosely) to aid the PCs (but not steal their thunder...that's always bad) so they come to see him as an ally.  We have one Wizard and he's very, very hesitant to use The Sight so that should be okay.  Its even easier to manipulate the PCs since Raveena's main goal is the ousting of the WCV in control of the city and things to this point have painted him as a bad guy.  Mostly because our PC WCV is his daughter and they are not on good terms...she won't even speak to him on the phone but makes other PCs call him when they need something.  So having an ally who is working towards similar goals but for very, very different reasons should make for an interesting few sessions.

Now that our group has gotten used to things (both in game and out of game), its time to start introducing some larger threats.  One of our City Themes is the struggle between long established power blocks (notably the white court) and newcomers.

While the WC holds significant political power and has ties to old, family run businesses, most of the newer interested parties tend towards sleek, modern business models (and in one case is tied to our city`s new convention center).  This is one such individual (and her goons).  Raveena is a Rakshasa, a magically adept shapeshifting creature.  Her preferred form is of an attractive Indian businesswoman (Raveena) but she also has a male alter ego (Kedar).  Her true form is unknown, it could be the multi-armed, multi-headed beast form she uses in physical combat, it could be the small, winged insect like form she uses for spying.  She is a skilled spell caster, but has no capacity for rituals.

Raveena/Kedar
Ravena
High Concept - Rakshasa Warlord
Trouble - Driven By Power

Aspects - Wisdom of the Ages; Drop Dead Gorgeous, Do Not Test Me, Scheming is second nature, Fiesty Little Minx

Skills
Average - Empathy, Might, Weapon
Fair - Alertness, Athletics, Rapport
Good - Lore, Presence
Great - Conviction, Deceit
Superb - Discipline, Resources

Powers - True Shapeshifting (-4), Evocation (-3), Modular Power (-8), Supernatural Recovery (-4), Catch (+3) - Total Refresh -7

Physical 00
Social 0000
Mental 0000

Raveena`s Goons are the Naga.  Human snake hybrids with venomous bites.

High Concept - Naga Goons
Other Aspects - Fast Fuckers
Skills -    Athletics: Superb
   Fists: Great
   Stealth: Good
   Intimidation: Fair

Claws (-2), Venomous (-2), Human Guise (0), Inhuman Strength (-2), Inhuman Speed (-2)

Combat Stats - Great Initiative, Superb Defense, Great Offense (+2 damage and venom)

Its ultimately your game and you're free to muck about.  For my $0.02 though, the player who chose to specialize in Thaum made their choice.  They have "lots of decent enchanted weapons" which should be their combat bread and butter. 

In my game, I use two different time lengths for exchanges in the case of magic.  Evocation uses the standard combat exchange (probably a few seconds).  Thaumaturgy uses exchanges of 5-10 minutes.  In theory you can cast a ritual in combat this way, but its going to require your buddies to hold off the monster for a few minutes, not merely a few seconds to buy you time.

When it comes time for a vampire to face her hunger, I understand that its a Discipline roll against an attack with a strength equal to the refresh of the powers used.  Is that a rolled attack or simply a difficulty?

Say our WCV uses Inhuman Speed (about the only feeding power she ever uses).  Does she roll her Superb Discipline against a Fair Difficulty or do I roll a Fair attack that she then defends against?