WOTC OMG 4E WTF?
Supposedly they are simplifying things to try to make the game friendlier to new players, and maybe win back some that jumped ship to Pathfinder and the plethora of home-grown OSR (Old School Renaissance) systems.
And of course nothing says simply like 5 new books and a handful of other new products.
It looks like they are simplifying characters by eliminating daily powers and tweaking how encounter powers work, and paring things down to 8 classes and 10 races. While things are supposed to be cross compatible, so you don't feel like you wasted the last $500 you spent on 4E, the new classes will not be the same as the old classes. So you need the new books.
Or you can tell them to sod off like I am doing.
You check out the info here. But I'd save your money and go here instead.