Pros
Opportunity – Working at HubSpot is entirely what you make it. You are given responsibility and in many positions, a lot of autonomy. Though what you do with them, is entirely up to you. There are few gifts (outside of the kitchen - ChubSpot), most things here are earned. You are expected to hustle, work hard, and solve for the customer. If you do those things, there are few limits.
Transparency - Want to learn how a SaaS product company actually works? You can see all the gory details here. The level of transparency and the willingness of the C-level folks to not shy away from even the toughest questions, but actually engage any and every HubSpotter is truly exceptional.
People – There are so many smart people here who are just really, really good at what they do and entirely willing to share their knowledge.
Benefits - The benefits here are ridiculous and just keep coming: ESPP, 401K match, on site gym (that's small but awesome), paid sabbatical, the use good judgment policy (yes, this is a benefit), free (great) beer, maternity / paternity leave, amazing coffee, solid Blue Cross Blue Shield with deductible coverage, and more free beer on the second floor.
Cons
It is very easy to get caught up in working too much here. The people who really excel, learn how to not thrash, but actually be productive with all that effort, and when they can and should dial it back.