Pros
The people are nice to work with, appreciative and bright. The work/life balance is respected and many people have a keen focus on diversity and inclusion. ARM focus on their strengths of solving tough problems and where appropriate use third parties and build success with partners. ARM don't try to do everything or win at everything. My perception is that ARM focus on an area they add value and then do a polished professional job of delivering it. The overall compensation is highly competitive - some of my team are starting to take their sabbatical's (4 week paid holiday every 4 years - only 3 years to go :-) I love the trust and autonomy. Despite ARM having over 4500 employees it does not feel like a bureaucratic machine. As a leader I can honestly say that there are few things which you must do in a particular way or slow me down. The processes are pragmatic and mostly there to be made up or tweaked to fit your purpose.
Cons
The nature of the work and lack of previous attention to diversity in team building has led to a narrow set of types of people you get to interact with. I appreciate ARM is taking steps to address this with a Project Everyone programme - I've got involved and hoping to see the positive impact over time. ARM was formed in Cambridge for designing cpu's. These are not cons, but they weigh heavily as perceptual baggage. ARM is rising up as a company in many world wide locations, who can develop world class software and become dominant in IoT. Despite this Cambridge and hardware sometimes seem to be the perceived places you must be.