Migrate from MongoDB to Postgres

Thinking about migrating SAVEE to use Postgres instead of MongoDB as the primary database. How screwed am I?

There's no performance bottleneck right now that would justify the painful transition. The only issue I've seen sometimes is when some references get lost. With Postgres (or MySQL or whatever..) you get foreign keys relationships that ensure this problem never happens.

But who am I kidding, I'm shitting my pants just with the thought of upgrading a minor MongoDB version on the production server hahahah

What do you think of this? Is it worth the hassle to use a more "grown up" database once you reach a fair amount of adoption? (SAVEE has 1.2M users, growing fast)