How can I check out Power BI?
If you want to check out the entire Office 365-hosted incarnation of Power BI, you can register to get in the queue for the preview now at http://office.com/powerbi. Microsoft will start churning through the queue in about four weeks. In the meantime, you are more than welcome to install the components you'll need on your machine to make it all work:
You can grab Power Query and Power Map from this location: http://office.microsoft.com/en-us/excel/power-bi-download-add-in-FX104087144.aspx. Note that the Power Map add-in still uses the old "GeoFlow" code name as of this writing.
You can, of course, get Power Pivot from http://www.powerpivot.com if you are running Office 2010 at present.