There are actually quite a few differences between EQ5 and EQ7. Not so between EQ6 and EQ7. EQ7 works exactly the same as EQ6, but with quite a few new features. I have yet to use any software with such a good manual, and the help files are even more complete.
I think that learning new software depends on individual skills. Since I'm the kind of person who learns best picking up a manual and working through the steps, that is how I learned to use this software (back in the days of EQ4). There was a learning curve with EQ5, but EQ6 was a breeze. Some people are more visual learners. I have never taken a class at Quilt University but would recommend it if you are that type of learner. I hear from many people that they have truly benefited from those classes. For new users, I would say take the EQ6 sampler class with Fran Gonzalez. Even though this is a EQ6 class, everything you learn there will apply to EQ7. And it is probably going to be a few months before they develop the classes for EQ7, so this is a good place to start.
Last, but not least, you may want to join the Info-EQ forum. This is a very, very helpful list of EQ users who are very quick to answer any questions. You can sign up on the Planet Patchwork website:
http://planetpatchwork.com/Mailinglists.htm
Hope this is useful!