Pros
Good if you are an autonomous person who doesn't need direction from immediate management. Very flexible environment although it can be extremely demanding at times if you work for the business side of the company. International travel to many interesting destinations as the company doesn't operate regionally yet. Great place to learn fast and work with the best engineers in the industry.
Cons
No benefits such as laptop or private health insurance. Lots of very skilled people leaving all the time, the company lacks an employee retention strategy. Senior management doesn't have a long term strategy and things may change any minute. Acting as a start-up in many ways but limited hiring also limits the execution ability of the current teams and burns out most people trying deliver quality, especially those coming from more mature companies used to have resources to do their job. Depending on the internal organisation you work for, the work-life balance can be inexistent, one must be ready to leave everything aside and just work for Canonical. It can be very frustrating to see how great potential and great opportunities can't be executed properly because lack of resources. In general, the feeling is a permanent chaos which doesn't seem to get better any time soon.