As MerricB pointed out, the difficulty rating replaces DC-setting - the only time a die is rolled is if skill rank = difficulty, in which case the DC is a static 15.Complexity Without Payoff: Hooray, everything now needs two elements to measure difficulty: a DC AND a difficulty rating.
In Burnning Wheel, say yes or roll the dice can be applied by the GM to him/herself - ie "There is no confict here, because that is impossible, therefore no dice need to be rolled"."Impossible": Do you for reals need a rating for something the DM just tells you you can't do?
HeroQuest has a "credibility test" in scene framing - which is to be negotiated between participants, with the GM taking the lead, and with genre considerations as the main constraint.
"Impossible", in Mearls' scheme, seems to me to occupy the same conceptual space.
No Surprising Results: So I guess I can't even try to be awesome with a good die roll? No? You're just gonna shut down my fun right there? Great. Thanks. Guess I'll keep chugging along on this railroad you've helpfully laid for me. Choo Choo.
I think LostSoul is right here. In addition, it seems to me that this sort of system could easily be drifted by allowing the "advantage ranks" or "penalty ranks" to derive from emotional/thematic factors rather than mere cleverness. (A bit like the bonus dice from Spiritual Attributes in TRoS.)I'd call "surprising results" a feature of skill systems that, when engaged, change the in-game situation in a pleasing and unexpected way. Is that what D&D needs in a skill system, though?
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You'll still get surprising results, but they will come from the player's ingenuity, not a lucky die roll. Focusing the skill system to make player skill an priority is a good thing in D&D, in my opinion.
So I don't see the railroading at all. In fact, by making the situation mechanically transparent to the players, it seems to me to facilitate them making meaningful choices.