Pros
Superb atmosphere and work/life balance. I found that the work-from-home schedule made a big difference in my overall quality of life and the humorously irreverent and collegial atmosphere made coming to work fun. It is a small company and your contributions matter and you know it. The company runs lean and it needs you to do your job and lets you do it. If you've ever worked somewhere that cluttered up your work life with impediments, then you know how important this is to your own job satisfaction. It mattered to me that the owners of the company were present and working as hard or harder than everyone else and were managing the company towards longevity and sustainability. The offices are in downtown Boston, a half block from the Boston Common, which is a bona fide benefit if you want to take advantage of what the city has to offer. It also means the weekly catered lunches and occasional off-site party are superior to what you'd get in a different setting. And right around the corner, the French Hot Chocolate at Thinking Cup is to die for.
Kontras
Working from home can be tough for some people but there are structures that prevent it from being isolating. Most groups have daily 'stand-up' meetings and you are connected with your coworkers via IRC and IM and voice-chat software.