Pros
You can work from anywhere, the vacation time is quite generous by US standards (4 weeks a year). Mozilla is big name to put on your resume that still gets some respect from recruiters.
Cons
There doesn't seem to be any paths for advancement in the company anymore. After two re-orgs (and four CEOs) in two years the company seems more interesting in putting the cogs into the places it needs them than it is finding a good balance between individual's career goals and the work the company needs to do. There doesn't seem to by anyone steering the ship, so different groups will often be working on the same problem without any collaboration or idea that anyone else in the company is working on the same thing. Pay for new comers is good, but the company doesn't keep up with the rising salaries in the tech industry and you will very quickly be making below the average salary in the industry, and the company is actively trying to keep employes below average salary for their position. With very few paths "up the ladder" your pay will stagnate pretty quickly.