Among the things I like about 3rd edition is the fact that + is always plus not -.
Explaining to a newbie that Chain Mail is +5 AC and since it is +2 magical and he has +1 due to dex and a base AC of 10 that his cumulative AC is 5+2+1+10=18 is relatively easy.
1st and 2nd edition for the same thing. Chain is AC5 add +2 for magic and get AC3 add +1 for dex and get AC2. Adding = subtraction?
Then to hit. 3rd Edition take your d20 roll add bonuses due to level, magic, strength (and any other bonus to hit from feats etc) and total them. Any penalties being negative of course reduce the resulting roll. For example a basic 3rd level fighter rolling 10 add +3 for level +2 for magic sword and +1 for strength. He hits AC 16 or less.
For the equivalent in first edition you have to look it up in a matrix. For 2nd it was slightly better but in both cases the adjusted number to hit bore no relationship to the armour class you hit. (Those numbers would I believe hit AC 4 or higher rather than lower in 1st and 2nd edition)
Now ability scores. What is the bonus for 15 strength? Dex? Wisdom? In 3rd edtion it is all the same. (+2 in that case). In 1st or 2nd it varies. 15 strength is no bonus but 15 dex and wisdom it is.
Of course if you have the old systems memorized it is easier to use them then move to the new system. If you are just learning the new system is far easier.
So why is 3rd edion bad again?
Actually I'm pretty young and was introduced to D&D. AD&D and 1e I got in...oh about 2 minutes. That entire THAC0 thing I understood in...oh about 15 seconds. Maybe I'm a genius, or maybe those who claim they don't understand it are either lying or complete idiots who don't know how to balance a checkbook, understand how to give me change if something cost 3.49 and I gave them 4.00, or understand the basic principle of if I have 20 dollars and use 5 of them to buy something I'll have 15.00 left (of course if they REALLY are that bad at math, I'd LOVE to sell them items that cost 2.00 but give them only 15.00 in change, afterall, if they really can't subtract something that easy...they are REALLY screwed and I could cheat the heck out of them).
I learned 3e and it was confusing as heck. If I wasn't playing with my uncle/cousin aka...family...arguments about whether someone got an AoO came up EVERY SINGLE FRICKEN session...NO ONE understood them really in 3e. Then they had all the full actions, standard actions, and a heck of other items. Then they have all these modifiers of which even I don't know half of which stack and which don't.
As I said, 1e and 2e took me...before I was even 18...oh about 5 minutes to learn, and THACO and AC all of about 15 seconds. 3e combat system took us MONTHS to iron out, took me several hours of reading and trying to figure it out to learn, AND then I had to figure out the skills system.
What's even more stupid was that they limit the maximum DEX in armor. Strenth goes up linearly instead of exponentially (either way) and a whole other slew of items for "balance" as opposed to none balance. I used to like playing 3e, but it's gotten inane. Especially when I figured that unless I was playing with my cousin/uncle, everyone I was playing with seemed like a rule...anyways I digress.
So though I can see that one might like 3e better, for this one who learned 3e, if you are a newbie, definately teach them some other system besides it. The only system I've actually run across that was tougher to learn than 3e was Rolemaster. Nothing was as tough to learn as 3e (edit: with as stated above, the exception of Rolemaster).
Now if you just want to play and not really know the rules, and let a Good DM rule you (such as...once again my uncle/cousin) then yes, it could be easy to learn to play...but to actually learn the rules...3e is dang tough for a player...much tougher than ANY system I've ever learned to play (once again with the exception of Rolemaster)...and that's coming from a newbie.
However it does appeal to some of the people of my age, the fast advancement, the gaining feats and skill points at each level...it's very fun, especially in computer games such as Knights of the Old Republic. But then the computer handles most of the rules (some of which are houseruled anyways, for the game) for you. The multiclassing, the equal advancement, and the min/max elements of the game are loved by many who play it.
And of course, if you buy into what WotC tells you, AD&D sucked, and no one liked it, no one will buy it again if they republish it in hardcopy, and they'd lose money, which is why they refuse to publish it anymore. (though after experiencing AD&D myself, I'm not certain I agree with their sentiments. I feel more like I'm playing an epic fantasy game akin to LotR or shannara, or otherwise when playing AD&D older editions. I feel more like I'm playing a fantasy game like diablo, Baldurs Gate Dark Alliance, or Final Fantasy when playing the new D&D game. I do like those games by the way...BUT, it is a different feel. I think the dynamics of 3.5 are simplistic if you don't really want to learn the rules, but waaaay to complicated if you want to know what you are doing in order to get a character that can actually face the CRs they throw at you, and even surpass the CR creatures if you get the right equipment amounts as per the rules).
My take on it, as perhaps one of the newer players of the genre. Unfortunately I don't have many of the older rulebooks except those I've been able to pick up here and there second hand, or read out of others.
I do have a full compliment of 3e books. When they switched to 3.5 I stopped buying them. I use the 3.5 rules with some groups but then I just use the SRD or use their books as I just thought the update was stupid...IMO. Especially coming so quickly after 3e. At the time I had a better allowance than most kids, and even I thought with what they did it was a waste of money. IMO of course.