Pros
Where do I start? The people and the culture are amazing. Before HubSpot I worked at a couple of Fortune 100 companies, did consulting for two years, and briefly owned my own business...none of those work environments came close to what HubSpot has. Apart from the people and the culture, the training and support is great, the pay is good, the perks are good and always growing (free food, in-house gym, etc.). As a high growth company career options abound, and lateral moves are common. I am in sales, and because the sales team in particular is growing fast there is good upward mobility as we add managers to keep pace with the team growth.
Cons
In the past I would have said work-life balance, but once I realized I was a borderline workaholic I was able to put limits on how long/hard I would work. My performance hasn't really declined (I was in the area of small incremental gains where the return for additional hours wasn't there) and I'm very happy with the balance I have struck.