Our goal is to allow WordPress community of site developers and designers to safely install Power Widgets in their theme of choice and benefit the amazing ease of use and value. Here are some themes we’ve been testing with Power Widgets.
  1. Twenty Ten
  2. Twenty Eleven
  3. Twenty Twelve
  4. Artisteer (both versions 3 and 4) generated themes
  5. Ithemes themes with Builder framework

Update (04 October):

Our most recent compatibility report: Power Widgets supports the additional following themes: Twenty Thirteen, Cyberchimps themes, Genesis framework child themes (Studio Press). Artisteer is supported with the current version and is expected to work flawlessly with the most recent version (4.2). We are currently working to enable custom post types and have Power Widgets work nicely with WooCommerce installed, and later on add theme compatibility to Woothemes themes. Theme compatibility now has a dedicated page which is being updated regularly.