Pros
The company culture is pretty good and management is mostly enlightened (all managers all the way up to and including the CEO are former engineers). Management does a great job of not getting in the way and micromanaging. They let you do the job you were hired to do. Their AReview system for gathering feedback on engineers and managers (which is an input into your compensation) is pretty well-designed to prevent people from gaming the system. The company has a good business model; it's a bit "enterprisey" for my tastes but what the company does provides pretty obvious value and the work is boring in a good way.
Cons
If your RSU grant performs well they use this success against you to argue against future raises. For example, after the recent jump in stock price I believe my RSU grant is now comparable with FAANG companies for a similar role but from Arista's point of view they think I'm making too much money. So I'm currently interviewing elsewhere because once you find greater financial success than your peers Arista is basically hunting for excuses to pay you less. It burns you out quickly to realize that no matter how hard you try or how glowing your feedback is management has no intention of rewarding you for going above and beyond until your financial situation falls back in line with they think it should be. Also, Arista will pay you less if you move to a lower cost of living area but they will not pay you more if you move to a higher cost of living area. This hasn't affected me but it has affected some of my coworkers. Not cool.