The difference is .5
Well, yes and no. There aren't huge major differences, and if you are just starting and taking an intro class, learning 2.0 won't hurt you.
As for Hibernate 3.0 versus the latest, you will see a difference in how you handle transactions, getting Sessions, and Exceptions. But, what happens if you get a job and their code is the 3.0 version, then that class is perfect.
I think the basics of Hibernate in 3.0 or 3.2+ is the same, and you will still get a good amount of value in that class.
But if it is the same money and you can find a newer class, then go for the newer classes.
Mark