Pros
A good thing of working in a startup company is the freedom and flexibility to build new things. Everyday I design and write code that make a direct impact in the product. The engineering team is composed of very talented and experience engineers, so not only I'm making an impact, but I'm also learning from amazing people along the way. The company is growing fast and totally trust our managers to take the right decisions and move it to the right direction. People in the company are very kind and helpful. We have a great culture and is is really a joy to spend time with them.
Cons
Being a small team we all have to wear several different hats. It's pretty common to have to lear a new technology or write code outside my comfort zone. It's nothing unexpected and also an opportunity to learn something new.