Huge career opportunities! It's one of the things I love about working for technology companies with high growth trajectory: you and the people on your team will have opportunities available to them like they would not at a static or standard growth company. It also allows one to fast-track their career to a certain extent. Now, this won't be easy - a fast growth trajectory means you have to put in the effort to get there.
Cons
As the company is in hyper-growth mode, finding the work-life balance can be difficult to achieve. The positive spin on this is management is very empathetic to these issues and recruiting is on a hiring spree to fill open positions.