I confess to disliking the tendency in later editions to reorganize character abilities to put all three physical abilities first. That always felt to me like they were prioritizing the physical abilities above the rest. Why that bugs me, I can't really say - but it does. Just a picky little peeve of mine.
Here's where I, as a DM, start to diverge from the rules as-presented - starting with the Prime Requisite. I don't use this concept in my own games as I am unwilling to reward a character simply for having a good die roll. Your reward for having high ability scores is having high ability scores. You have a better chance of success and that does not translate to deserving bonus experience during the course of adventuring. Again - this is just me. Something else I do differently is to have all ability score adjustments range from -3 to +3. I never saw a reason for Charisma to range from -2 to +2 for Reaction Adjustment, for example, where just about every other ability adjustment went from -3 to +3. Probably my first attempt to streamline the game. Call me a tinkerer.
Character classes. Ahhhhh...the section where my heart first started to pound with excitement. I confess that I first thought of Tolkien when I was reading this section - and no surprise there. Except for Clerics, you can pick out every listed "class" from the Middle-earth setting. Why was "class" in quotes back there? Because Moldvay Basic presents demi-humans (Dwarf, Elf, and Halfling) as classes of their own. Because D&D was intended as a human-centric game from the start. And, why not? While Tolkien had an obvious influence on the early D&D game, there were so many other classic fantasy references that gave us other iconic bits and pieces of the system. But I digress.
I also run on a bit. Let's pick this back up in the next installment, where I'll talk about my views and variations regarding the various PC race/class options.