I'm decreasing a lot of DCs that seemed to be unreasonable before, but it's a trial and error process. Still, I haven't had the chance to test the system above level 5 yet, so we'll see.
As for the balance, I think they are reasonably balanced, but there is always room for improvement. Obviously, if there is a combat encounter, those skills that are used in combat are used much more frequently, and there are a few skills (like Deftness) that don't see much use (even though they are now much broader than before).
Here are some examples of skill use from tonight's session (which was combat heavy - one big combat against 6 CR 3 lizardfolk fighters and one CR 7 lizardfolk cleric; the party is comprised of 4 level 5 characters):
Acrobatics - the druid wanted to wild shape from her bird form back to humanoid form in mid-air (close to the ground), so I asked for an Acrobatics + Dex check for her to pull it off and land safely.
Athletics - the fighter wanted to use a Fate point to push his two companions out of danger, so I asked for an Athletics + Str check to see how far he was able to push them.
Expression - once they reached the castle, the bard wrote a very detailed report of their journey and future goals and offered this report as a sacrifice to his deity (patron of knowledge) during prayer; I asked for an Expression + Int check to see how well he related the information and awarded him a minor divine blessing.
Healing - after the fight, the druid spent an hour using Healing to treat her companions' injuries, managing to heal most of their wounds.
Insight - I asked for a group Insight check to see if the party would figure out that two in-game events were related (they failed).
Intimidation - the fighter used Intimidation to assist his overrun.
Perception - after the fight with lizardfolk was over, the mage and the fighter tried to spot one of the escaped lizardman within the murky lake to finish him off (they failed).
Persuasion - the bard persuaded the guards to let the party into the castle in the middle of the night
Streetwise - the bard recalled some specific details about the Duke and his wife (they were traveling to the Duke's castle)
Survival - the fighter used Survival to lead the party out of the forest, and his good check result reduced the random encounter chance (they still had 2 random encounters).
There were numerous Acrobatics, Arcana, Brawl, Earthlore, Endurance, Expression, Marksmanship, Melee, and Resolve checks during combat (which took up about 2 hours real-time, and I'd say about 7 rounds in-game; didn't feel grindy in the least bit, though - players were on the edge of their seats the whole time).