I have worked with many product managers on a product vision exercise. In my observation the place where the product managers get hung up the most is when they confuse product vision for product definition. To use an analogy, product vision is a trailer and product definition is a movie. When you're watching a movie trailer it excites you even though you fully don't know how good or bad the movie will be.
Abstract and unfinished
A trailer is a sequence of shots that are abstract enough not to reveal too much details about the movie but clear enough to give you the dots that your imagination could start connecting. Some of the best visions are also abstract and unfinished that leave plenty of opportunities for imagination. Product visions should focus on "why" and "what" and not on "how" and most importantly should have a narrative to excite people to buy into it and refine it later on. Vision should inspire the definition of a product and not define it.
I am a big believer of raw or low fidelity prototypes because they allow me to get the best possible feedback from an end user. People don't respond well to a finished or a shiny prototype. I don't want people to tell me, "can you change the color of that button?" I would rather prefer they say, "your scenario seems out of whack but let me tell you this is what would make sense."
Movie trailers are also the best examples of non-linear thinking. They don't follow the same sequence as a movie - they don't have to. Most people, product managers or otherwise, find non-linear thinking a little difficult to practice and comprehend. Good visions are non-linear because they focus on complete narrative organized as non-linear scenarios or journeys to evoke emotion and not to convey how the product will actually work. Clever commercials, such as iPad commercials by Apple, follow the same design principles. They don't describe what an iPad can do feature by feature but instead will show a narrative that help people imagine what it would feel like to use an iPad.
Means to an end
The least understood benefit of a product vision is the ability of using the vision as a tool to drive, define, and refine product requirements. Vision is a living artifact that you can pull out anytime during your product lifecycle and use it to ask questions, gather feedback, and more importantly help people imagine. I encourage product managers not to chase the perfection when it comes to vision and focus on the abstract and non-linear journey because a vision is a means to an end and not an end itself.
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