Hi,
one of the biggest problems with 3.5 was the book keeping. This means the big ammount of buffs in higher levels. Not mentioned the problem when you where hit by a dispel magic spell and the amount of time you need. The same problem is with monsters. To many abilities, feats ...! Though, at higher levels combat will need much longer to play.
Hi!
Welcome to role playing. :-) You should look at Hackmaster - Armor damage, ammo counts, incrementing segments in combat. It's full of 1e type book-keeping.
If you're into low book-keeping you might try a system like FUDGE or something. (can I say that without getting into trouble?)
I feel you on this one. I've run two by-the-book 3x campaigns through 20th level, and boy-oh-boy do they suffer from complexity creep.
Here's what I did for my third game -- I boiled stat blocks down to the absolute minimum (HP, AC, resistances, Saves, list of actions), and only kept whatever powers/abilities I thought the baddy might use in 3 rounds of a fight. Meteor Swarm? Keeper. Change Self? Not so much.
Less is definitely more.