I'm going to disagree with some of the prior posters. I think the Dresden Files RPG is an unplayable train wreck.
The world, of course, is awesome. But I hate FATE and I think it doesn't work for the Dresden-verse at all. The first major issue with the game is the layout of the book. Its sort of designed to explain the game as you read it. But then they start referring to stuff you haven't read about yet which makes it so confusing I think their approach fails.
And the layout of the book is a nightmare to find anything if you need to reference a rule in play with critical information buried in the text and scattered throughout the rulebook.
My other issue is the system itself. You need Fate points to really be effective at anything because everything in the system depends upon you spending them and spending them frequently. And thats one of the big problems.
In theory, you are only supposed to need them to boost yourself from competent to good, or even awesome. In practice, you need to burn through fate points just to even be competent at things you should be able to do, let alone spending them to be awesome. Even with the GM letting them flow like water, the players felt like they were barely competent for about half a scene before completely sucking for the rest of it.
The FATE dice also adds too much variability. Now matter how good or bad you are, a roll can take a 1 to a 5, or vice versa. And once again, you need to burn through Fate points just to keep the dice from screwing you over, let alone actually spend Fate points just to be cool.
Then there is the damage system. Way too binary and way too deadly. A hit is either totally inconsequential, or your are staring at your entrails on the street in front of you. In the books, Dresden regularly takes on and survives foes tougher than he is. In the game, a single ghoul can TPK your whole party in no time. Its just ridiculous. And yes, that happened in our game.
Finally we decided we had enough and converted our game to True20, a ruleset that is vastly more suited to the Dresden-verse, than FATE, IMO. And we had a lot more fun after that.