Biggest downside: a lack of established process. Big corporate had too much process at times, but there was normally decent enough tooling around everything. And there were teams to do everything, which really allowed you to focus.

Advantage: More control over what tools I use. Always something interesting happening, and knowing that the growth of the company is directly influenced by your work.

I am also terrified that being able to impact the company/culture means that I will lead us down the wrong path.