Pros
This was my first software development role. Because of the small size of the business and low experience level of my team, I was meaningfully contributing within days, and soon was involved in every part of the software development process, granted about as much responsibility as I was willing to take on. This was a huge asset to my growth. Openness and communication were a fundamental part of the company culture, and it was a very warm and cooperative environment that attracted a team that was very easy to work with.
Cons
While initial growth was fast, it was capped very quickly. Due to the small size of the business, there wasn't really a second rung to the ladder. The team I was working with was very inexperienced, so there was little in the way of senior expertise to draw on.