One of the great aspects of 4e is it officially recognized retraining. Finally, we had a formal rule for the process of substituting a power or a feat. In previous versions this aspect of the game was either forbidden or house ruled. Now, the concept itself isn’t a big stretch. The idea of swapping this power for that one isn’t new. What is new is the recognition of the game creator to enable this as an official rule.
I’m well aware that many other gaming systems have had such rules for a long time, but D&D has not. Now, you might be wondering what’s the big deal. If I’m not happy with my character I’ll simply change it or speak with my DM about the problem. Fair enough and in most instances a change is able to be made. What happens if you only play RPGA games though and you don’t have a real mechanism to make the changes you desire because a new source book has been released?