Pros
They not only take care of the typical benefits (medical, dental, vision, etc.) but they also add in a daily lunch stipend (I haven't paid for lunch in a little over a year at work), commuter benefits, unlimited PTO, and so much more. Outside of the awesome perks, management makes it extremely apparent that they are here for your career progression. They will work with you to make sure you are progressing the way you need to in your career. From the top down, the culture of putting the community first, growth, and working together as one overall team is absolutely apparent. It really is an awesome company to work for.
Kontras
This isn't necessarily a "con", but change is a consistency at Upwork (in regards to business focus). Be prepared to pivot.