I work for a medium sized engineering company which only has a couple of applications that are used outside of the company. And both of those were actually developed in-company first and then marketed outside the company so we definitely do eat our own 'dog food'. This is both good and bad, as our internal users are very conversant with the backing theory used by the software but our external users fall into two categories: 1)users that know MUCH more than our average internal user (an 'industry expert') or 2)'casual' users that just want to know enough to use the software for their limited purposes. We get very good feedback from internal users and external 'industry expert' users but the real gold is from the 'casual' users because these users show us where we've assumed knowledge on the part of the user just because that knowledge is common internally. It's important that the feedback from these 'casual' users is not treated lightly by thinking 'oh, that's stupid, everyone knows that'. So, while it's very useful to have the internal use and I firmly believe that companies should use their own products, don't ignore the feedback from the 'real world' either as they tend more to think outside the internal user's 'box'.