My friend and colleague, Stever Robbins, has started a blog, and one of his early posts is Are engineers living on another planet? Don't they use their software?
Unfortunately, not always. It takes self-discipline and the desire to look for problems to cause people to create systems that allow them to use their own software. If a project team only builds once a week, they're not going to use their software. If they fix a bunch of defects at one time, the testers can't do a complete install and test pieces in isolation. Instead, the testers need to install the whole darn thing and test everything together.
The current phrase for using your own software under development is “eating your own dog food.” (Anyone know the origin of that phrase? I'm fairly sure I was using in the 80's, before Microsoft popularized it.) It's not easy to use the product under development. And, it's a great idea.