Founder of RudderLabs (RudderStack now) here. You nailed it - Control, Cost & Privacy (Data-Ownership) are the main drivers we have seen in people adopting us. Kind of related to Control is the whole drive to adopting open-Source technologies. We engineers always wanted open-source but increasingly larger enterprises are interested too - maybe to avoid vendor locking or maybe just because cool engineers (who grew up adopting open-source stuff) are finally getting into decision making positions.

Shameless plug - we wrote a blog on setting up an Open Source Analytics Stack with one of our deployments highlighting these issues.

https://dev.to/rudderstack/how-to-build-an-open-source-analy...

PostHog looks awesome!! Congrats on your launch. Would love to collaborate and share notes.