The UI in versions prior to this could be a little bit daunting for new users with lots of buttons, icons and multiple browser windows open. Dynamics CRM 2013 has adopted a SPA, single page architecture, with a more responsive and cleaner user interface.
A new type of form called Quick Create has been added to Dynamics. There is a clue in the name and Quick Create forms allows you to quickly enter the minimum information required to create a new item from another form. In the screen shot below if you click on the + link on the opportunity sub grid the Quick Create Opportunity forms appears.
In addition the create activity functionality introduced in Polaris has been extended.
Be aware there is no way to revert to “classic forms” from 2013.