I recently switched from Django 1.6 to 1.7, and I began using migrations (I never used South).
Before 1.7, I used to load initial data with a fixture/initial_d
In my opinion fixtures are a bit bad. If your database changes frequently, keeping them up-to-date will came a nightmare soon. Actually, it's not only my opinion, in the book "Two Scoops of Django" it's explained much better.
Instead I'll write a Python file to provide initial setup. If you need something more I'll suggest you look at Factory boy.
If you need to migrate some data you should use data migrations.
There's also "Burn Your Fixtures, Use Model Factories" about using fixtures.