A great example of a good use of screenshots is HN member pxlpshr's company Salt Lick Labs ( http://saltlicklabs.com/ ). He is only marketing the iPhone apps, but there is a level of polish that makes you want to see more, even though you know you don't actually need to read about peoples' horrible relationships or to catalog your own relationship endeavors.
The gaming company Blizzard is known for their delays in releasing games, but they are also more known for having the sharpest, most intuitive user interfaces and game play out there. Take this ideology into consideration when preparing a service like OverTrainer (something I'm actually interested in using). Build it to work, but don't show it until it makes people think, "Wow, I need to get involved n this product/service/community."
The gaming company Blizzard is known for their delays in releasing games, but they are also more known for having the sharpest, most intuitive user interfaces and game play out there. Take this ideology into consideration when preparing a service like OverTrainer (something I'm actually interested in using). Build it to work, but don't show it until it makes people think, "Wow, I need to get involved n this product/service/community."