Pros
Xero was a enjoyable, young company to work for and I did enjoy my time there. It's full of incredibly smart people who all work as hard as possible together to get stuff done as best they can. Rod is an energetic, down to earth CEO who actually interacts with you as an employee and remembers your name.
Cons
Despite the way that Xero pushes itself in public, it is not a "fun" place to work in the traditional startup sense - it's enjoyable indeed, but more corporate these days, which isn't necessarily a bad thing. There are no real organized activities that improve the culture aside from the yearly parties, at least in the office I was in - much of the culture is hyberbole over what it's really like, simply for marketing purposes. There were also few growth opportunities - middle management blocks attempts to move across teams inside the company for political reasons and the company is unwilling (or unable?) to offer many professional development courses (often only providing tickets to events to the management layer). I've watched both of these happen over and over again to myself and co-workers who eventually gave up and left rather than waiting around to move inside the org or get a promotion. It sucks to have to go through this yourself, even more to see it happen to your co-workers too. There are also some middle management issues right now and the company continues to hire more and more middle management to try and solve it which made it increasingly harder to get work done. It is now very political and corporate; no longer startup culture.