At the end of the day, the slide boards are a great tool when used properly, but they should be seen as a catch-all replacement for all of your other speed and conditioning methods.
The slide board is a tool that was originally designed to be used by speedskaters but is now being used by a wide variety of sports — hockey being the most popular outlet for its use for obvious reasons. Incorporating a slide board into your training is just like any other tool in strength and conditioning, meaning, there is a right way to do things and a wrong way to do things.
The major problem I see so prevalent in the hockey training world is that parents and coaches utilize tools rather than skills. For example, if you need a handyman, it would be wise to find a very skilled carpenter. A carpenter has the skill development in order to use a wide variety of tools and chooses to select the correct tool that will maximize the effectiveness and efficiency of the job at hand.