There are a lot of changes, as this is with most new editions.
This is not EXHAUSTIVE...
1: Character creation is simpler. Skill are divided into Basic and Advanced and use abilities as base rolls.
2: the Resistance table is gone. Certain skills are used to to resist things.
3: Less use for calculators.
4: Parry and Dodge are no longer weapon skills.
5: Book format is excellent. Easy to understand and well organized.
6: Total hit points are abolished, hit points get taken directly from the limb - there are degrees of wounds.
7) Strike ranks are done a little different.
8) Combat actions are introduced (Letting you do so many things in combat)
9: Hero Points let you change things in the game or give you greater powers throughout your characters life (Legendary Abilities)
10: Magic Points are still there.
11: Core Rule book covers Rune Magic Only - They also added runic abilities when one Integrates with a rune.
12: Companion Brings back Sorcery and Divine Magic. Cults of Glorantha II Brings back Shamanism (Spiit Magic). Magic Of Glorantha Brings Dragon Magic and sorcery for the god learners.
Hope this encourages you to buy the book or you can download the SRD'd from the Mongoose site. They will more direct rule changes.