Hi, We tested it carefully. While comparing it with browser. Live Desktop takes 15 - 17 where as firefox takes 108.4 as the energy impact :). Avg impact is just 2 where as Firefox takes 6.
CPU Firefox 55.3 where as Live Desktop is 3.8

Yes we are working on multiple monitor support as many customers as asked for us. We are happy to do it in next update. We are also working on some of cool features in next updates. Thanks so much for taking your time to write to us. We will do this :)

Dear Life Hacker and Thorin, We will never forget this day. we worked day and night for this moment, featuring in life hacker is a huge moment for us. It will be framed. Thanks so much for taking your time to share with wonderful mac community.