Without getting into specifics, here are my changes:
1. Skill points for all classes, but at slower rates (non-specialists get a single point every 2,3 or 4 levels, and have a specified skill list). These points can be substituted for a to-hit bonus by elves and dwarves.
2. Saving throw improvement curves are "softened" and distributed across levels. I've made new XP charts for all classes to accomplish this.
3. Some new skills (Medicine, Lore and Riding) and an old skill removed (Open Doors, which is treated as a simple strength check). Medicine opens for First Aid, which means a party can get by a bit without clerical healing.
4. MU magic retention - elves and wizards can keep spells memorized upon casting by making a magic save modified by Int, but take a host of risks if doing this (I have a number of simple charts to reference, basically they can take damage or be stunned for small amounts of time, or if trying this with high level spells they can be feebleminded or - yes - they can of course die).
If people are interested I can post specifics, but this is most of what I've wanted to change. I often play with inexperienced players, and thus try to add as few loose rules as I can; especially to combat.