Small company and building means cabin fever kicks in fast.
Busy work during slow business waves, means doing something outside of your job scope, often. But this can be an advantage, because they recognize it. Senior management is highly qualified to be there.
Small company means you aren't getting experience in a large business environment, and that shows at interviews. Also, pay is great, but not fortune 500 pay. And you may get very far, but you aren't doing it at a large corporate office, so again, you might being comparing apples to oranges at a fortune 500 interview. But with skill in interviews, this wont matter.