Completely different. If you're invested in 3e, you're probably going to hate it. It's basically its own game under the D&D label - More of an alternate D&D direction than a continuation. If you can get past that, though, I think it's better.
It is more video-gamish in combat style, but I think in a good way. Your powers mean you can always do something cool - It could be the same thing you did last round, but that depends on the tactical situation, as it should.
For example, against the animated statues, I mostly used Eldritch Blast because it was the highest-damage and it's Charisma vs. Reflex. But, I also tried Eyebite after one of them fell down, because its secondary effect is a round of invisibility versus the target and I was right next to it - The one it would attack when it stood up. Didn't work, but that's not a fault of the rules, I just rolled low.
(That's another change - You basically have six attack values (Your attributes) and four defences (AC, Fort, Reflex and Will) - Which means no more constant wiffing versus the high-AC monster; you switch around attacks until you find a weak defence. Tactical, as it should be.
Against the skeletons, Dire Radiance saw much use, as undead are vulnerable to radiant damage and Dire Radiance does an extra d6 if your opponent moves closer on their next turn - And it was a maneuver battlefield. And now that the game is over, I'm realizing there's other tactics we missed that we could have used.
And that's another thing. There's not a single class that you *Need* to have to succeed. All of our characters were support characters and while the cleric did keep us all from dying, so could a warlord, a paladin or even a fighter to soak damage and deny enemy advantages. (That's another thing. Clerics are far more than a heal-bot and fighters can do a lot more than 'I attack')
Contrary to some doomsayers, spontaneous actions that don't depend on powers are not out - They may even be easier. (Roughly what happened) Wizard: 'I use mage hand to fling the lantern at the hobgoblin'. GM, maybe ten seconds later (Realtime): 'Roll Intelligence versus Reflex'. Roll failed, but again, not a fault of the rules.
And customization of powers? I looked at about 8-10 random powers of the same level and was able to mix, match and balance them by eye in seconds. Only one of the new powers actually seemed to need balance work.
But yeah, buy it and form your own opinion. I'd suggest you play a session, too.
And, as a warning, you won't be able to make the exact same character. The same type of character, yes, but not the exact same. Barbarians, Druids and Bards aren't in there; neither are half-orcs. However, the classes will be making a reappearance in additional books. (Can't remember about the half-orcs, but probably them, too).