Pros
There are enough free food, amenities, and parties that you never need leave campus. Everybody is friendly. Lots of things to work on.
Kontras
All housing near HQ is priced for the top wage earners at Google so you can't buy a house and renting will eat your entire paycheck. Google's coding environment is designed for the lowest common denominator and twisted to support a nearly infinitely large codebase. 95% of your time will be waiting for spaghetti code to build, fighting code review trolls, following Google code style, trying to figure out bone-headed non-standard architectures, debugging your Google-modified world, wading through endless obsolete documents, and dealing with the politics of egomaniacs pushing their dumb new framework/storage/language/whatever in an attempt to gain recognition within a nearly infinite megacorp. Google uses almost nothing from the outside world so almost nothing learned can be applied to your career elsewhere. There are insufferable KoolAid guzzlers saying they love the "startup culture," as if it was normal to write 100 lines of code in a day, wait a week for it to be committed, and then attend a party of 1000 strangers texting while a computerized DJ blasts retro pop music. For all of this effort, regardless of the official project title, what you're really doing is enabling the creepy collection of marketing data.