It is coming soon - today or tomorrow. I shall not be able to have internet access tomorrow therefore I write preliminary comments.
The engine has a number of very interesting features:
1. You enter a query in natural language. It means that you do not need to think about keywords and can get more relevant search results. It means more deep search as well.
2. When you get search results you easy see not full document or webpage but highligted sentences that are relevant to your query.
3. You see semantic environment of your search results. It means that you see a content of the document and you see both related terms and actions you can do for more relevant search.
4. You can select and click the new term or action and then you will see the relevant part of the document or webpage in the content at the right of the document.
5. Powerset team used very nice friendly and interesting tool for collecting feedback.