My uncles got me DND version 4. I love it! The rules are very different, though.
Spells:
Spells are no longer the vancian spell system. You can still memorize them, but its different. Some spells can be used once a day if you memorize it, some once per fight if you memorize it, and otehrs at will memorized or not, but at 80% power if not memorized.
Fighters:
There is a solid difference between sword, mace, and axe fighters…they have different abilities available.
Wizards:
No more fireball spell
New races…Dragonborn and Tiefling, and no more gnomes.
There are fewer “save or die” spells.
Dragons are a LOT tougher.
You can do more with your turn.
Bards, barbarians, and monks are gone.
Warlock class!!!
New rules for disenchanting and enchanting magic items.
I love it!