I've reviewed Diptic in the past. It's a great iPhone app for creating photo collages on the fly. Now, Diptic PDQ (US$0.99, universal) gives you many of the same features with a new look and a quicker workflow.
The developers call it a "stripped down" version of Diptic, but don't let that fool you. Diptic PDQ has the same wide feature set, but far fewer design templates. While Diptic has 200, Diptic PDQ offers just 35 templates.
It's easy to manipulate your image within the frames for the best composition, and you can adjust the size of each frame. Images can be zoomed and rotated, and reversed for a mirror image. Borders can be customized by color and size. There are 14 filters you can apply to your images.
I made some impressive collages with very little trouble. Your collage can be saved to your camera roll, sent via email or uploaded directly to Instagram, Twitter or Facebook. Although the output is advertised as high-resolution, my creations were just over 1.4 MB, so it's clear they are being compressed when mailed. I'd like to see a higher-resolution option. Filters apply to all images. I think it would have been better to have the ability to apply them individually. Collages are limited to four photos. I didn't find the reduced number of templates a limitation. There were plenty of options to suit my needs.
Diptic PDQ is perfect for quickly creating vacation photos, or pictures from a social occasion like a party or meeting. People you send them to will appreciate how nice they look.
Diptic PDQ requires iOS 7 and is optimized for the iPhone 5, and presumably the iPhone 5s, which has the same screen specifications.