Pros
BEAUTIFUL office space, excellent work-life balance (in my experience, nearly everyone is gone by 5:30 at the latest), opportunity to advance, fast growth (many new faces). This isn't the kind of company with free lunch and dinner everyday and ping pong tables in the office. It's a place you go to do work that you hopefully enjoy (although we do have company lunch once a month and a themed company-wide happy hour each month as well). There are channels to bring your own personality into the company as well (art night? rock climbing? let's set it up!). Women are well represented on all levels (rare for a tech company). And last but not least, Lew Cirne and Chris Cook are some of the friendliest, hard working, and dedicated people I've ever come across.
Cons
New Relic is going through some growing pains right now-- no longer a "fun" young startup, but moving towards a more mature company (more policies, middle management, etc.). Lots of meetings for management, sometimes difficult to get time with. Remote employees may feel disconnected from the main offices.