That's a matter of opinion. I found the explanation in the DMG clear enough - perhaps because I was already familiar with HeroWars extended contests - and was able to implement it without much trouble.Skill challenges were dismal in both explanation and implementation.
The aspect of skill challenges that I found tricky follows from the GM never rolling: when you want to narrate an active opposition, this creates questions as to how far you can go in narrating what a PC does as part of your own framing and narration of consequence. There is - unsurprisingly, I guess - a resemblance to Apocalypse World here. I have seen posters on these boards object to the GM narration in the AW rulebook example of play ("Moves Snowball") because it includes narrating things about how the PC responds when the NPCs turn up at her house and throw a grenade into it.