The great thing is that even while Lost Photos is still digging through your account, you can start looking through old photos. You can control the thumbnail viewer at the bottom with your arrow keys, and click any picture to view a larger version. There are also options to post a photo directly to Facebook or Twitter, or attach it to an e-mail using your default client. You cannot, however, share multiple photos at once.
As clean and simple as it is, Lost Photos' interface is also its biggest pain point. The thumbnail viewer accommodates only four photos and can't be resized to add more. Now, imagine my displeasure at having to use this tiny panel to scroll through my 1,000 photos. It's easy enough to view downloaded pictures in Windows Explorer or Mac Finder, but still, the interface could use some major improvements. It would also be nice to have a few sorting options in there.
Usability issues aside, Lost Photos is an awesome app. It performs as advertised, and is perfect for anyone with one or several e-mail addresses. In any case, I can almost guarantee the app will come up with some old pictures that you completely forgot about. Whether that's a good thing or a bad thing is another story.