Like a lot of players I grabbed the 2e books as soon as they came out. The art was good, they layout improved in a number of ways, and the books were well-made.
As for the rules?
- The concept of changing from attack charts to THAC0 so players 'get the math' was a good idea, IMO, and I always loved watching the light dawn as someone realized how it worked and all that this implied ('I hit with a 14 but not a 13? Boom! I know it's armor class!').
- Cleaning up the classes and moving them around a bit was interesting and mostly good. I remember having a lot of talks about assassins in particular ['they are just hired killers. Anyone can be an assassin' vs 'it is a specific class']. While I love the monk I know why having monks in the game is An Issue. The addition of the Bard as a class was interesting and got rid of the meta-issues of the 1e bard. Removing the cavalier and barbarian of the UA was a a solid move.
- Specialist mages was very popular at the time and allowed a lot of people to add a lot of color and depth to a lot of campaigns. The additions from the Complete book and especially the further specialties of the Spells & Magic book made AD&D magic much, much more varied and erased any idea that all spellcasters are somehow the same!
- The addition of clerical spheres and then kits radically transformed how clerics were seen, especially by the sorts of people that needed to read this. Add in the options from Spells & Magic and clerics really became radically different and much more flexible.
- The ability of thieves to customize the advancement of their thief abilities is a HUGE difference and a very welcome change! As a friend of mine previously complained,
"Oh, you have a Halfling thief with a 16 dexterity and the backstory that he grew up in a rural community,learning stealth in the fields and meadows as he hunted rabbits with his sling? Cool! Another player has a Halfling thief with a 16 dexterity and the backstory that he grew up an orphan in the slums of a major city picking pockets to scrounge enough to eat? Cool! Guess what? They have the exact same chance to pick a pocket!"Second edition fixed that - you could finally have thieves that focused on just stealth or just traps - it was great!
- Non-Weapon Proficiencies (also known as Skills) were a great addition to AD&D. A lot of DMs I knew had added them from the Survival Guides or (most often) from Oriental Adventures but having them in the core books and better integrated into adventures and supplements was a great add-on to the game.
It also alleviated some of the weirdness that many players went through of 'No! ONLY rangers can track. At all. Ever.' Or 'Do you know how to make a spellbook? Uh....... No?' Suddenly there were mechanics for what your characters could do not directly related to their class in the core rules.
- Making the most common house rules/omissions 'legal': How many DMs that aren't me ever enforced material components? Making them optional was just accepting general play. So was upping demi-human level limits and increasing the possible multi-class options.
Let's face it, while you can borrow back and forth, AD&D 2e is a different game than AD&D 1e; and that is OK. But far too often I think 2e gets lost in the shuffle or dismissed. The reality is this:
AD&D 2nd Edition is a fun, playable game that is a great part of the D&D family.
Maybe it's best feature is you can have two characters that are the same race, same class, same level, even the exact same stats, and yet have them be very different in abilities and roles because of the use of non-weapon proficiencies and kits.
That is a great feature, isn't it?
That is one of the reasons that my second-longest running campaign (almost 8 years!) is AD&D 2e with all the Skills & Powers books.