Wow I can't believe I read this whole thread. Tho it's been more of an interesting read with less on how editions changed and more on "what can a commoner do and what they can't."
My thoughts.
Commoners suck. I say 3 HP, AC 10 and they can do what you want them to do be it farm or make beer. Experts make goods and provide services beyond commoners but are not "rogues without sneak attack" as some would have them be. Thats how I approached that particular situation in Bard's Gate. I.E. If an NPC is more than a farmer or wagon driver then they must be an expert. Likewise im pretty sure the rules state somewhere (in some edition) that class atrophy can happen. Thus "Once great adventurers" who now run shops are now maybe a 3rd level fighter/4th level expert reflecting their change in occupation. I'm of a mindset that you don't need to over-explain that stuff to players who are looking for adventure, loot, and hookers.
Speaking of the last: I'm a DM who prefers RP to die rolling to get thru situations and thus hate diplomacy/bluff/intimidate and the sort and use those only in a situation of "last resort". When it comes to the latter: Make the die roll, because I'm not interested in the pervy details that an immature player may be looking for to satisfy their "RP Needs".
That said Over Rolling can be just as abusive as the "antiquated" DM Fiat.
Others have done a pretty good job summarizing the variant changes from edition to edition, and folks have weighed in on what they liked about previous editions vs. new. Mostly its a matter of taste.
I agree with those who feel that the CR system IS lame. I don't like crash helmets and air bags in my games but thats my choice, just as the choice of how you run is yours and yours alone. Who or what your players' characters' run into is also your choice. How they react to it is theirs. The CR system offers a model and yes, it happens to be a model i "generally" use for printed product. However, It's not necessarily what I use when running the adventure as I find most pampered characters are a significant challenge to MOST monster or trap encounters of up to 5 levels above their supposed threshold. Likewise some bad die rolls or insipid RP on their part during these encounters could result in their demise. The difference being, I let the players know this up front.
I don't rail road them and I leave everything open ended enough for them to find canny solutions to difficult problems. Then again, everyone has their own way of running and style of play, which is what makes the game great in the first place. I guess I would have "preferred" an option where you could get CR OR FLAT xp. If PCs want to go "Dragon Warrior" and kill green slimes for xps so be it.
Final Thoughts
It's a stone bummer that a couple of you had really crappy DMs when you were kids. Your grown now so maybe some day you can stop blaming Gary or some wicked "Gygaxanistas" for your wretched 1ed experiences. He wasn't running your game, some other nitwit was and they did you wrong. Come to terms! (Said with a grin and not with an ego whip).
If he had been running your game, you would have been having fun. Who else pushes back their thick glasses, wiggles their fingers in your face and says "Bibbity Bobbity Boo" when the evil wizard crackles you to cinders with a lightning bolt after the entire party through use of bad tactics collapsed like a flan in the cupboard? I tell ya, you would be too busy laughing to care. Then again maybe not, but heck, I was.
Shark: You're welcome at my game table any day bro.