A LOT of DM's add in House Rules to AD&D 1st Edition - and that's fair enough, we've all done it.
Whether its leaving out Weapon to-hit modifier tables, weapon speeds, or Class restrictions. The Tables and Weapon speeds can be cumbersome, unless your brain works in such a way that remembering them is a snap.
Weapon Speeds I only really bother with in Cases of Tied Initiative anyway, and though detailed I can't remember a time when I used the Weapon to-hit mod tables anyway.
Class restrictions are useful and important (if a game-world isn't human-centric, if its ruled by Demi-Humans I would put restrictions on Humans and Half-Breeds personally) and one of the best things in Unearthed Arcana is the expanded Race/Class/Level Tables - that would keep even the most ardent Demi-Human player happy for a long time). Plus with the use of Wishes, intervention by Deities, and other Cosmic Influences - you can elevate your non-Human PC's to the levels you want them to be without destroying World balance - people who want to play Demi-Humans without restrictions in my experience are power-gamers anyway, they want extra abilities without any penalties or effort on their part. To them I say table top rpg's aren't for you they should stick to playing PC/Console based RPG's where they can cheat easily and get the power rush they want/need.
Harsh - of course, I'm a tough DM. I roll ALL my Dice in front of my Players too - no fudging of Dice-Rolls for me, I let the Dice lie where the fates put them. For good or ill. As a DM I practiced total honesty with my players, and (without being egotistical) they loved and respected me for it.
When I ran A LOT of Games - not just once in a while, often three times a week - I had to turn people away from sessions. Once we had a decent number of players (I like 4-6 personally, you get a good solid group dynamic that way) that was it. I've ran for groups as big as a Dozen players, but you can't focus on story and character development in the same way - and the games become all action and no substance, and whilst fun are tiring and in the long term unsatisfying.
Linda (my partner) was great, she even played till we had Kids. Even after our Daughter was born, she would help out with Drinks and Biccies LoL - I remember one morning she came down, the curtains were closed and it was late Autumn, we hadn't even realized the time. Linda sweetly said good morning and fixed everyone Tea and Toast for breakfast!
Back to House Rules, the only other big House Rule I introduced were "Con Hits" - the first big part of it is the use of Constitution instead of the "-10" when you reach Zero Hit Points. It makes lower level Characters much more durable, although I have always given Max Hit-Points at first level personally.
When you reach Zero Hit Points all Damage is then applied to the Constitution of the Character. When accrued Damage takes you down to half your Constitution Score, your Character falls Unconscious (and is seriously in need of treatment). When your Character reaches Zero Con - sorry, he or she is Dead (and in need of a Priest LoL).
Lastly unless you REQUIRE a 20 to hit, a Natural 20 when rolling to hit means the Damage is applied directly to Con (rather than double damage or what have you) - this of course REALLY makes higher level characters less cocky.
What about Con for Monsters - easy. 9 plus number of Hit Dice. Of course Dragons are Monstrously tough, but then again they should be IMHO.
Con-Hit's do not work against Constructs either (no Con, sorry you just have to hack these buggers apart).
You cannot "Con-Hit" Creatures of twice your height or More - simply mechanics really - they are either too tall, their hide becomes too thick etc. This of course left a "gap" in the Magic Items table, which meant we could have Weapons that allowed Con-Hit's on Giants, Dragons, Demons etc, etc . . . .
That's the thing about AD&D 1st Edition, it was SO easy to add/change the things you needed too - more modern editions (of any game to be frank) are so tightly interconnected rules-wise its really very hard to make things work the way you want/need them too (fingers crossed for D&D Next LoL).