As one of my players has showed me, it's easy to fix. Post-errata skill challenges always require three failures to... fail. (Non-errataed challenges required a varying number.) That sets up a handy system for degrees of success.
- Success with no failures: Flawless Victory! As a DM, you'll probably want to throw in some bonus if the players manage this.
- Success with one failure: The baseline. If you are using pre-written skill challenges, the default result of a success can probably be substituted here.
- Success with two failures: You succeed, but there is a setback.
- Three failures: Failure. What it says on the tin. Pre-written skill challenges can have the default failure result inserted here.
The astute reader who's familiar with skill challenges may have noted that one can add "degrees of failure" based on how many successes the party got before failing. Unfortunately, the required number of successes varies, so it's not quite as straightforward. For me, four degrees are enough, but I might suggest a fifth:
- Three failures with no successes: Ballads will be written about this utter defeat. Don't expect this one to actually happen, the probability is pretty low unless the party is taking on overleveled skill challenges.
Let's do an example. The PC:s are hitting the library books before facing down some Elder Evil which is supposed to return to the world at the next solstice (in three days).
- Three failures: The PC:s find nothing about the Elder Evil. They'll just have to play the fight by ear when it arrives. In addition, they have drawn the attention of the Elder Evil's cult. Some cultists will interfere in the upcoming battle.
- Two failures: The PC:s find out where the Elder Evil will arrive (near a site sacred to Dagon, which is the temple ruin outside town), and basic information about it, but draws the attention of its cult.
- One failure: The PC:s know where the Elder Evil will arrive and basic information about it.
- Three failures: The PC:s know where the Elder Evil will arrive, and also finds some notes by a priest who fought it eons ago. (OOC, the players get to know its vulnerabilities and resistances.)