For what it’s worth…
I actually got started playing with 2e, though the group I first played with used a hodgepodge of 1e and 2e (I think they’re pretty compatible, but not being particularly familiar with 1e, I don’t really know) with some Arcanum thrown in.
So, with 2e coming back into print, the debate resumes on the merits and flaws in 2e.
People who prefer addition to subtraction don’t like THACO. Still, it’s easy to convert descending to ascending AC and just note your Attack value based on 20 – your THACO. (Oh, crap, that involves subtraction!) I’ve heard that there are people who dislike THACO for other reasons. I don’t know what those reasons are. THACO was simply introduced to eliminate the need for an entire combat chart when really you could extrapolate all the information you actually needed from a single column.
I don’t remember if 2e got rid of 18/xx or not. If it did, go it! I don’t remember seeing anything in 2e’s core that was particularly annoying that wasn’t already in 1e. Proficiencies were basically the same as feats, and I guess if you really hated them, you didn’t have to use them. Proficiencies never came up in the games I played. 3e had all of its skills and skill points, but that always felt to me like taking all of those % tables, giving them a bit of flexibility and going around and making them mandatory (fun fact: they’re not!). Then, there are splatbooks. If you can’t concoct your own specialty class on your own spare time and get your DM to sign off on it, you don’t need to be playing it.
I think a big issue people have with 2e is cosmetic. The books are ugly and the art is bland. The books have the binding, paper, and overall feel of Houghton-Mifflin textbooks. Most of the art felt cold and scientific; a fighter and his gear laid out much like a diagram of a dissected frog. If the rules for 2e had ever been repackaged in a more visually appealing format, I don’t think that it would suffer the disdain that has become so attached to it.
2e has a sterile feel to it, which in part was a reaction to the satanic panic and the overall image problem that D&D was gaining due to journalistic malpractice, but in many ways, it was still the same game mechanically. 1e was Snakes & Ladders. 2e was Chutes & Ladders. 3e was Mousetrap.
In the meantime, I think this is a good time to point out that WotC has still avoided publishing BECMI or the Rules Cyclopedia. I’m not saying this is a bad thing. So much of the edition warring and debate focuses on 3e vs older e, or anything vs 2e, oft forgotten is the old Basic Edition. The beauty of Basic was that the entire game was self-contained in a single (or two, with B/X) booklet, without the need for multiple core books. However the eventual release of the long promised Companion (which didn’t cover what Expert said it would cover), Master (oh, god, who would enjoy playing at this level?), and Immortals (has anyone actually successfully played the Polymath ascension path to its conclusion? If so, I think I’d like to punch them) took what was a pretty well balanced, functional system and threw sense out the window with its massive scaling problems and absurd cosmology. I mean, if you’re going to have to come up with a new table of demi-human related attack classes based on tiered XP, just take the damn level caps off.