What were the major effects of the New School Design changes?
No particular order
Experience for Combat"When the party defeats monsters, the DM awards them Experience Points." 3.0 Dungeon Masters Guide, Page 165
It's not that simple of course. They receive awards based on the challenge of the trap or monster overcome. When is a challenge overcome?
"As the DM, you must decide when a challenge is overcome. usually this is simple to do. Did the PC's defeat the enemy in battle? Then they met the challenge and earned experience points. Other times it can be trickier. Suppose the PCs sneak by the sleeping minotaur to get into the magical vault--did they overcome the minotaur encounter? If their goal was to get into the vault and the minotaur was just a guardian, then the answer is probably yes. It's up to you to make such judgments." 3.0 Dungeon Masters Guide, Page 165The major effect on play? The game's advancement is driven by combat, where you are assured of acquiring the experience you need. The option for it to be based on 'goal' behavior drives hoop-jumping and railroading. The intent is good, i.e. "you can gain experience for things besides killing monsters", but the actual result in play makes the game much more combat oriented, because that is where experience is guaranteed.
Saving Throw Difficulties are based on the Wizards Power
"The difficulty class of a saving throw against a wizard's spell is 10 + the spell's level + the wizard's intelligence modifier." 3.0 Players Handbook, Page 53
A 7th level fighter in 1st edition has a base save of 10-13, giving him a 55-40% base chance of saving versus any spell. It would not be unusual at that point for him to have a +2 to +4 bonus on a variety of saves, pushing that up to a 70-80% success rate.
WARNING, 3.0 Math: That same fighter in 3rd edition with likely equipment is going to have a base +2 to +5, with equipment and stats providing +2 to +6. This means their total bonus ranges from +4 to +9. But now the wizard has the choice to target their 'weak' saving throw with his spells! This means 1d20 + 6 versus 16-22 (assuming a 16-18 stat range for a +3 to +4 bonus and a third or 4th level spell for another +3 to +4 bonus) Along with the fighters magical equipment, it is also likely the wizard may be focused in that spell (+2) or have a piece of equipment raising his stat by 2 or 4 (+1 or +2). I am not unaware of 'Iron Will' and 'Lightning reflexes' or the 100 tricks to maximize the various things. This is assuming the basics, resistance bonus, stat enhancements, and spell focus. END MATH
Best case for the fighter? 50% success rate. Worst case? 20% success rate.
Suddenly save or die/suck became a whole lot more deadly.
Feats, Prestige Classes, and Unequal Power
"Prestige classes allow DMs to created campaign-specific exclusive rolls and positions as classes. These special roles offer abilities and powers otherwise inaccessible to players. . ." 3.0 Dungeon Masters Guide, page 27
Want to trade in your ability to turn creatures for extra actions? Want to do tremendous amounts of damage? Looking to break the game math in new and interesting ways?
Well, you can, by picking feats and prestige classes. But you can't just pick them - you have to have all the prerequisites. How do you meet the prerequisites the quickest? Well, you have to make all the right choices at the right time. You've got to build your character.
Old school classes required much fewer choices, and the choice they did make rarely depended on the choices they made before.
Standardization of Effects and Wealth by Level
"You can create a potion of any spell of 3rd level or lower that you know and that targets a creature or creatures." Brew Potion Feat from the 3.0 Players Handbook, Page 80
"Table 5-1: Character Wealth by Level is based on average treasures found in average encounters compared with the experience points earned in those encounters. Using that information you can determine how much wealth a character should have based on her level." Character Wealth, from the 3.0 Dungeon Masters Guide, Page 145
A strict reading of the rules of course indicates that anything could be in a potion bottle, but the effect of the above, meant that potions, and other magic items, became known quantities. Far easier to have each effect be a standard one easily referenced and similar to all others.
And this is true. You do spend less time having to look things up because everything works the same. However, everything feels a lot less magical.
Hack & Slash