Hiya.
WARNING: Long...
All of these diatribes by Mr.Mearls keep nagging at me. His reasoning seems...inexperienced? I guess that's the closest way to put it from where I stand. At any rate, most of his 'ideas' aren't anything new; they've been out there for decades in various rpgs and campaigns. What keeps bothering me about his articles is he seems to be all about the "absolutes".
I see him write
When you climb, you must be standing up and have both hands free. and my first reaction is...Bad Designer! No twinkie for you! With that very first sentence he's set an "absolute". In a game like Monopoly, Chess or Poker...absolutes are fine, if not needed. But this is a role-playing game. Using such language is always, IME, a *very bad* thing. I immediatly thought of a two situations that would simply not be allowed by this RAW; a character treading water in a pit (not standing), or a character laying prone in a small sinkhole as nasty critters grab his legs and try and pull him into their earthen lair (not standing). What about someone who his holding onto an uncounscious halfling friend (two hands not free)? You get the point. Using "absolutes" is best avoided if at all possible.
Next is his use of a single ability to govern all aspects of a skill. Again, not the best idea, and one that screams lack of experience. Climb, in his new skill version, uses Strength. Period. As if someone with a 16 Str, 4 Dex and 5 Con could climb as well, fast, and constatnly as someone with 16 Str, 14 Dex and 15 Con. Again, IMHO, a missed opportunity to get away from D&D's current "uber stat for XXX skill" problem (ex: in 3.x Fighters are better climbers than Theiv...er...Rogues are). By brancing out to even 2 stats (say, STR and DEX), the've reduced the likelyhood of a one-stat-wonder having crazy-good ability in some skill by simply taking '1 rank' in it, beating out the average stat guy with multiple ranks in it.
When he starts to get at the obvious...a skill gives you a bonus...all is fine. That is, until he gets to the whole "skill talents" thing. Then he's right back to square one, with the absolutes. Just look at the first 'climb talent'.
Cautious Climber: You never fall when making an ability check to climb. If you fail a climb check, you still move half your climb speed.
Absolute = BAD DESIGN...even if it's disguised as a 'talent'. What if a player says "I'm going to move at half speed and be very cautious so I don't fall". I know that I, as any self-respecting DM, would not be able to look the player in the face and say "Uh, no. You don't have that talent".

This kind of rule writing will result in very 'numbers-and-absolutes' role-playing styles. You know that kind; where the players say things like "I just jump into the 20' pit, ignoring the tightrope, because I don't have the Tightrope Walker talent I can't even try it, so may as well just jump in now." Not cool for keeping the tone and suspension of disbelief in an RPG.
His whole blurb on "Layers and Complexity" is rendered pointless simply because he has already set up 'absolutes' on what the climb skill allows (or disallows) PC's in the game to do. So, even if a DM decided to go "light" and not use the Skill Talents, for example, the nagging "well, if we were using the skill talents then my guy could at least
try to do this...".
Sorry, Mike, I'm going to have to give your rule design a solid C-. It may work, but it won't be particularily good or fun.
^_^
Paul L. Ming