Pros
Work/life balance is great, the environment is relaxed, the team is really friendly. You're given plenty of responsibility without being micro-managed. Advancement within the company is very open-ended and really just depends on how ambitious you are - I moved up to a pretty high position (from being an assistant) after just 6 months, so it's really about how committed you are to tackling new challenges and learning new skills. If you demonstrate those traits, you can move up really quickly.
Cons
On the admin side, you have to be really comfortable wearing a lot of hats at the company, even if something doesn't technically fall under your department. Over time I've grown to appreciate this - everybody has each other's backs, and I always have a diverse array of projects on my plate so I'm never bored! - but it definitely took a while to adjust, and you really have to be open to learning new things that you may not have expected.