Thumbstacks is like a simplified version of Power Point. The main difference is that the application is entirely online and you can easily share it with others via the Internet.
This system is great for students who want to continue working on a project from home or from a computer in school that is not setup with Power Point. It's also great for schools that use Linux. While Open Office has a presentation tool, it may not be a good choice for students who want to work from home -- parents may not want to install the massive Open Office suite for a few presentations.
One issue I saw with Thumbstack is that it does not appear to important and export to Power Point or to any other formats. They say they are available anywhere there is an Internet connection, but what if you loose the connection? It would be nice to have a copy on the hard drive.