Once you are over the shock, though, you realize that Dynamics CRM 2013 helps you improve the user experience, and eliminates complaints about the "clickiness" of Dynamics CRM.
Another benefit is that Dynamics CRM 2013 includes features in its user interface that required coding in earlier versions of the product. Want multiple versions of forms? mobile forms? conditional fields? All these are in there without the coding required in say Dynamics CRM 4.0.
So when you upgrade to Dynamics CRM 2013, analyze before you convert your code -- you may not need it anymore. If you end up making your 2013 version look and behave the same as it did in 4.0 or 2011, you're doing something wrong and not taking advantage of the features of the latest version.