Pros
You get to work with some of the industry's best. And not "work with" like you see them once a year, but "work with" as in you're on the same team. The caliber of people here is just outstanding! The company really respects its employees. Individual opinions, time, work-style - all are valued. This leads to this being a great place to do work. A lot of procedures in place are there to minimize overhead and repetitious tasks - hence a phenomenal build system, automated test infrastructure, and the most painless merge / mergeback setup I've ever used. I feel like I'm learning a lot every day (2 years and still going strong). It's really humbling to look at the more senior people and see how much more I have to learn! The company is working in a really rich sector which is quickly growing. The company is growing really quickly and that presents a lot of career growth opportunities. There's a strong drive towards internal promotion instead of external hiring whenever possible. We actually sell something you can touch! This may seem foolish, but selling something real, something where your software actuates a physical action, is really rewarding. Leadership has done a great job of keeping the focus on Engineering rather than managers. All of the managers here were engineers first, and accepted a management position because they made good managers, but also because they saw the need for oversight and direction, and agreed they were the best person to provide it. Management seems to view its role as "getting out of the way of software engineers so that they can do what they do best - engineer software" which leads to a very healthy culture. Very open culture at all levels. Engineers talk with Jayshree around the coffee machine, a weekly beer-bash encourages people to mix and meet with others from around the company. Arista is in it for the long-haul. When asked if we were firmly committed to an IPO as an exit strategy our CEO responded no, that's our *entry* strategy; we're not here to exit, we're here to change datacenter networking and you can't do that if you just exit. Wide range of Software Engineering from firmware and EE-style register twiddling to very high-level programming. Solid mentoring and development opportunities 20 days/yr of PTO for everyone. Weekly beer bash!
Cons
Arista wasn't founded by web2.0 kids and the perks don't shadow those companies: there're no free meals (although the snack bar is pretty darn good), no subsidized gym memberships, no on-campus dinner, no massages, no laundry, no daycare, etc. It's a workplace, and not a place to live...IMHO that last one is actually a pro but individual mileage may vary. You won't be made an instant mega-millionaire instagram-style because that's not the game Arista is playing. Most of your friends will have no clue what you work on. You can't pull up a website and show them. Most of the time you'll settle for something like "we make the internet work" and move on. On a day-to-day basis the work isn't super-flashy: it's just solid, interesting problem solving. (more of a neutral than a con)