Pros
It pays well and it has a lot of resources to support big projects. Many of your coworkers will be smart. A few will be brilliant.
Cons
Most of what you hear about working at Google is just hype. The reality doesn't live up to it. Shitty passive-aggressive middle management. Systematically rewards only short term results, which leads to exponential compounding of code cruft. I mean they give explicit instructions for calibration and promo to consider only demonstrable benefits of the last 6 months of work, and nothing earlier than that which had a delayed benefit. So the rank and file are forced to be like shitty mutual fund managers obsessed with quarterly results, in contrast to the upper management's supposed long term focus. When you start they flip a coin and if it comes up tails you are stuck in ads for years against your will. 20% time is a lie. 20% time is essentially unpaid overtime and if god forbid your 20% time takes a risk and fails you will be calibrated as if you had spent that time doing nothing. Every creative idea is shot down in favor of the same old safe but inefficient crap. All the projects come from the top down. There is no bottom-up innovation in ads because they try to keep everyone 110% busy with top down mandates. The company hasn't really innovated much in years. All their fast growing products are acquisitions or "me too" and the ads infrastructure is bloated and ossified. There's a lot of witness-tampering when it comes to peer reviews and stack ranks. You aren't allowed to rate your experience working with a person. You're supposed to somehow rate their entire accomplishment including stuff that you had nothing to do with. And if your stack ranks differ greatly from your manager's opinion of the latter they will passive aggressively hint that it will be a reason for firing you. Valve has a much better stack ranking system where people just rate their own experience working with a person and all feedback is anonymous. Also unlike Valve, Google has no freedom of association with whatever projects you want to do. It's all top-down mandates and selfish horse-trading by psychopathic middle managers. I've read about the toxic culture that killed Microsoft and it sounds very similar to Google in my experience. A lot of the managers were hired from outside the company and tracked their shitty culture in with them. Perhaps that explains it.