The Photomerge feature is not just for panoramas anymore. The detection and blending technology in Photomerge has been enhanced to make all your photo-merges easier to create, and there is are two new types of Photomerges you can create. Photomerge Group Shot helps you combine multiple photos with groups of people so you can create one photo where everyone is looking their best. Photomerge Faces is a just-for-fun feature which lets you combine facial features from 2 different photos. While Faces is a bit of a gimmick and doesn't give very good results, the Group Shot tool is excellent and could justify the upgrade price for many.
In the screen shot here you can see where I have two photos opened into group shot. They are automatically aligned, but the alignment tool lets you tweak the alignment if necessary. Then you can transfer elements from the source photo to the final photo simply by swiping across them with the pencil tool. If you make a mistake the eraser tool lets you remove merged areas.