The top change 3e made to the D&D spell system...

[DaveMage]

My favorite change was the elimination of progressive casting times.

Nothing worse than having the wizard go last (and usually hit beforehand) because he was casting a high level spell.

 

[smetzger]

...was the ability to prepare a 3rd level spell in a 4th level slot if desired. (Or just cast, for sorcerers).

I think there are more siginficant changes than this.

Being able to cast a spell in melee.
Being able to leave a spell slot open.
Metamagic.
Counterspells.
Bonus spells for Wizards.
Switch to only 3 types of saving throws.
Spellcasting attribute effects the save of a spell.
Free spells in your spellbook when you advance a level.

 

[Darkness]

Shorter spell preparation time. In AD&D, high-level casters took very long to prepare all their spells.

Also, the ability to prepare spells "on the fly" if you can meditate for a short while.

 

[Geron Raveneye]

...was the design of the sorcerer's charisma-based magic, in my opinion. It is set off wonderfully from the studious wizard, limited but flexible in it's own way, carries a lot of flavour, and branched off into hybrid systems like the Arcana Unearthed magic system.

Clerical spontaneous casting is a nice idea, too, I just wish they hadn't done it with healing spells, but with domain spells...but that's house rule stuff. The principle is neat.

All the other points are good, too, because they raise the flexibility of D&D magic while staying true to the original system.

 

[Thanee]

Top change is spontaneous casting.

Bye
Thanee

 

[johnsemlak]

i thot the big change was in the 5 H's.

polymorph is still messed up too.

5 H's?

 

[diaglo]

5 H's?

Hold X
Haste
Heal
Harm
Holy Shiite

 

[Klaus]

Heal, Harm, Haste... uh... did I mention Haste?

 

[teitan]

I really like the further tweaks that Monte Cook made in Arcana Unearthed, making the magic system not only smoother but more customizable and useable. Very sweet system that I would LOVE to see make it into regular D&D.

Jason

 

[Eremite]

Saving throws.

One of 3E's best changes, full stop, IMO.