As to the main question - Should companies 'eat their own dogfood' (use their own products) - absolutely. If they are not using their own but something else, then as a customer (or potential customer), I would likely ask them why I should not use that other product as well. (assuming they are comparative)

There are some pitfalls with doing this if you come to think of your internal user base as indicative/representative of your users in general. Normally, this would be inaccurate - unless your userbase is primarily other software development firms (unlikely for most). Using your internal users as additional testers is fine, but not to the exclusion of traditional focus groups, useability testing and other requisite methods.

The biggest challenge I continue to face deals with what is now called the Paradox of Choice (which leads to feature creep). Many seem to think in terms of 'more is always better' - when in many(most) cases, streamling or even removing some features is better than adding 'stuff'.