Just as many Attacks have been updated from the Sixth to Seventh Generation, so has many older items from many previous generations of Pokemon. Most of these items have decreased in their given values, but some have actually been made better.
Updated Items:
Aguav Berry: It now boosts health by 50% Max HP when Pokémon drops below 25%
Figy Berry: It now boosts health by 50% Max HP when Pokémon drops below 25%
Fresh Water: Hit Points recovered dropped from 50HP to 30HP
Hyper Potion: Hit Points recovered dropped from 200HP to 120HP
Iapapa Berry: It now boosts health by 50% Max HP when Pokémon drops below 25%
Lemonade: Hit Points recovered dropped from 80HP to 70HP
Lure Ball: Capture Rate has changed from *3 to *5 when catching hooked Pokémon
Mago Berry: It now boosts health by 50% Max HP when Pokémon drops below 25%
Nest Ball: Capture Rate modifier has been changed to (8-0.2*(level - 1)). Minimum 1
Net Ball: Capture Rate modifier has been changed to *3.5 rather than *3
Power Anklet: Effort Point boost has changed from +4 to +8
Power Band: Effort Point boost has changed from +4 to +8
Power Belt: Effort Point boost has changed from +4 to +8
Power Bracer: Effort Point boost has changed from +4 to +8
Power Lens: Effort Point boost has changed from +4 to +8
Power Weight: Effort Point boost has changed from +4 to +8
Repeat Ball: Capture Rate modifier has been changed to *3.5 rather than *3
Soda Pop: Hit Points recovered dropped from 60HP to 50HP
Soul Dew: Now only boosts Latias' & Latios' Psychic & Dragon-type Moves by 20%
Super Potion: Now recovers 60HP rather than 50HP
Timer Ball: Capture Rate modifier has been changed to (1+.3*Turn Number). Maximum 4
Wiki Berry: It now boosts health by 50% Max HP when Pokémon drops below 25%
X Accuracy: Increases the Stat by 2 stages rather than 1
X Attack: Increases the Stat by 2 stages rather than 1
X Defense: Increases the Stat by 2 stages rather than 1
X Special: Increases the Stat by 2 stages rather than 1
X Sp. Def: Increases the Stat by 2 stages rather than 1