Pros
SUPPLY.com is a company that's at the crossroads of a new startup and an established company. As an employee, you get the best of both worlds - job security and benefits (health insurance, 401k, etc.), but also the chance to wear multiple hats and make a big impact. Few companies give young people the opportunity to own projects and processes like they do here. Your success at the company is wholly dependent upon you, but if you "crush it," you'll be rewarded with even more responsibility and the opportunity to broaden your skill set. It's like steroids for your résumé.
Cons
Like any rapidly-growing company, there can be times that feel chaotic. If you're someone who wants a job where every week is the same, this isn't the right place for you.