If you don't have a local store in your area to try these out yourself or you didn't get to try all the features because the battery was dead at the store, then I think this site is a great idea that may help you take a more extensive test drive of a device you are considering. Some devices are not even available at local stores and these types may appear on TryPhone in the future as they are planning to continuously add new devices.
I personally plan to use the service for myself since they also provide device specs in a nice format. Their service also has reviews, tutorials, and demos of the devices. You can also send feedback on one of the virtual devices or request that they add a new phone to their offerings. I look forward to seeing this site continue to grow and have it now bookmarked.