I thought Unity was pretty rad at the beginning of the year but for the money I think Shiva is amazing. I've been using the PLE and it's all straight forward. You never have to leave the IDE. You can browse the web with it, script with it, and do your level design with it ... brilliant! In addition StoneScript is as simple and intuitive as Blitz3D. For anyone who's worked with Torque and Blitz this seems to be the great compromise. I was eager for Unity but it ran like crap on my Mac Mini and I also prefer to develop in Windows, it's more productive.