CRM Online is updated to Polaris, main feature is the cross browser support.
We are all waiting for that, no? You all have tested in an other browser, Chrome, Firefox, yes even safari maybe? There is also the ipad support, Microsoft is releasing it mid February.
This trick is unsupported, but you also want a preview no? Just take the url of your online environment and add /Main.aspx to it.
Just Like this