Thats...a lot of changes, and not simple ones, either. For starters, magic missile now always hits but deals less than half damage than before, dispel magic becomes an encounter spell, and lead the attack only lasts a turn even if you hit. And thats just a few of the changes out of Player's Handbook. All told you're looking at 20 pages of errata, so I'm glad that Character Builder gets updated as well. This means that unlike 3rd Edition I don't have to print out the pages (or check the interwebs) so that I can reference them when making a character.