How do you strike the balance between educating users, showcasing new features, and driving continued product usage through content in the post-launch phase?

It's all about segmentation. In another answer here, I suggested a dual-axis approach to segmentation (attributes x adoption). On the attribute axis, start with whichever attributes are most relevant to your business or specific launch, ie plan tier, company size, etc. On the adoption axis, use product usage data to group users, ie power users, sporadic users, inactive users. Each of these groups may see different values in the new feature based on what type of customer they are and how they actually use the feature/product.

It could look something like this (9 different segments based on plan tier and usage patterns):

Inactive Sporadic Power
Good 1 2 3
Better 4 5 6
Best 7 8 9

Think: What message, content, or call-to-action will resonate best with an inactive user subscribed to our entry-level Good plan tier? What message, content, or call-to-action will resonate best with a power user on our Best plan tier?

If a customer is already a power user of your new feature, they don't need more education. Go ahead and encourage them to use other valuable features that they may have overlooked. Better yet, ask them to share a success story with the new feature.

If a customer has been inactive and your goal is to get them to use this new feature, perhaps showcasing other customers' successes with the feature will get them to take the leap and log in to check it out.

A sporadic usage customer may just need more education. They're aware of it. They've used it. But they haven't fully adopted. Why? Perhaps they don't see the full value or are still struggling to understand how to use it.

This is always the hard part! However, I find it best to think of your current customers and prospective customers as different audiences. So, what channels can you reach your prospective customers? I usually look at the channel map and assign each a goal - so an in-product notification may drive product usage, emails may educate users, and social media and blog may showcase our new features.