I've been running the D&D Next playtest rules, and I am still trying to come to terms with the skill system.
My criticism of skills is that the proficiency bonus just isn't substantial enough. At Level 1, someone trained in a particular skill is a mere +1 better than someone who has no experience whatsoever. I realize that the math and DCs of DDN are lower overall, and a +1 in DDN is not the equivalent of +1 in 4e or 3.5. Nonetheless, it still doesn't work for my group and I. We just don't feel like these characters really are trained in the skills, both from a mechanical and a storytelling standpoint. And even moreover, the random die roll really is the main factor in whether or not you succeed at a task.
Look at a skill like Arcana, for example:
Level 3 Mage, Arcana +5 (+3 INT, +2 prof)
This conveys that a mage's wizardry training has only made him 10% better in the realm of arcane lore and magical knowledge. Sure, pure raw ability plays an important role in any skill, but one's training and dedicated learning should play a much greater role. This is especially obvious in very specialized areas, such as esoteric lore, device disabling, or even baking; think about it- your training is practically everything.
Let's say the 3rd-level party comes across a magic rune in a dungeon (DC 15 Arcana). The mage has a 50% chance of identifying its properties, while the fighter has probably a 25% chance. That's a noticeable difference, but really, it should be a bigger difference. Like, mage 60-70% vs. fighter 5-15%.
I could think of many, many more examples where the implications are that one's raw ability and (even more so) pure chance play the biggest factor in determining success. I shake my head.
Furthermore, why does the proficiency bonus have to be equal for attacks, spells, and skills. Would it really be that difficult to create a different bonus (like +5 to +11) for skills? I seriously doubt that a shift of 4 points is going to break the bounded accuracy philosophy.
Lastly, Rogues. The Expertise feature suddenly makes it feel like you are actually trained in skills again but, only this one class receives this feature. Mages aren't experts in Arcana, Clerics in Religion, Druids in Nature, and so on. It don't know if WotC is going to implement such an update in the future, as I've heard nothing of it, but I seriously hope the skill system gets revised.
May your adventures be many and your diligent training make a difference,
Esper