A 10th level 3.5 specialist Wizard might have these spells:

Cantrips-Dancing Lights, Detect Magic, Ghost Sound, Light, Mage Hand, Mending
1st-Burning Hands, Color Spray, Mage Armor, Magic Missile, Shield, Shocking Grasp
2nd-Flaming Sphere, Invisibility, Mirror Image, Spider Climb, Summon Monster II, Web
3rd-Dispel Magic, Fireball, Lightning Bolt, Manyjaws, Stinking Cloud
4th-Ice Storm, Invisibility-Greater, Orb of Force, Summon Monster IV, Wall of Fire
5th-Blink-Greater, Cone of Cold, Wall of Force

While a 10th level 4e Wizards might look like:

At-Will
Ghost Sound, Light, Mage Hand, Prestidigitation
Magic Missile, Thunderwave
Encounter
Burning Hands, Shock Sphere, Fire Burst
Daily
Flaming Sphere, Expeditious Retreat, Stinking Cloud, Levitate, Mordenkainen’s Sword, Arcane Gate
Rituals
Comprehend Language, Make Whole, Tenser’s Floating Disk, Eye of Alarm, Water Walk,
Detect Secret Doors, Enchant Magic Item, Knock, Travelers’ Feast, Brew Potion, Cure Disease,
Raise Dead, Disenchant Magic Item, Leomund’s Secret Chest, Remove Affliction, Water Breathing,
Wizard’s Sight, Consult Mystic Sages, Detect Object

Comparisons
The 3.5 wizard had at his disposal 4-8 area attacks that could do 10d6 (35 avg)
While the 4e wizard has 3 encounter spells that do 2d6+6 to 3d6+6 (13-16 avg) and 3 Daily that do even less

So the 4e wizard goes from about 35 to 16 average damage
Plus the monsters on average have about 3 times the hp, so its really like going from 35 to 5

To add additional insult the wizard will likely miss half of the time, halfing his effectiveness yet again.

Very very lame. Guess the designers were all sword swinger types.

I do like 4e Flaming Sphere, Mordenkainen’s Sword and Mage Hand. They would be fun to play around with.

But the wizard just doesn't keep pace with the other 4e classes like the Ranger for example.
Ranger can do 2d10-3d10+6+1d6 to multiple targets. He can easily average around 21-26 damage it looks like.

Other Impressions

We played most of the Keep on the Shadowfell module. The battles took forever, mainly because the monsters have 3x the hitpoints and the wizard is nerfed. I DMed, the players said picking up the rules was easy, but they seemed to get bored with their options quickly. The party would have been TPKed on at least 3 encounters if I hadn't fudged the monsters attacks and tactics. The options all seemed to be the same for everyone, just the names changed, just whack away. None of the cool effects ever lasted long enough to be interesting or a challenge. Effects would last 1-2 rounds tops before a save.

Minions are just lame! They look like there was a huge hole in the game mechanics, and minions were a half hearted attempt to cover it with a quick patch. This Ogre has 1hp and the next one has 111hp, lame. No Ogre should ever have 1hp!

After reading the powers for a while they all just started to feel the same, only the names changed. Same damage and toss in something random (shift, move, slow) to make it seem different.

Feels kinda like more whack-a-mole and less a RPG.

The wizard wasn't so much over-powered as the fighter classes were under developed and boring. They needed some additional powers and abilities. Which 4e provided. But the rogue, cleric and new PH2 druid were easily a match for the 3.5 wizard. So instead of fixing the fighter, they fixed and fighter/ranger and nerfed most of the other classes. Made the solution much more complicated than needed. Getting rid of bonus and specialist spells would have helped bring the wizard down a notch Like the idea of giving the wizard a spell or two that never run out, the 4e at-will powers. But then again, a magic missile wand does pretty much the same thing.