How traumatic is to migrate from struts version 1.2 to struts version 2.0 ???

[Ariel]

Hie everybody:
 I have a project working with struts 1.2 version, I would want to know How
traumatic is to migrate from struts version 1.2 to struts version 2.0 ???

Thanks in advance.
Greetings
Ariel