The 1.6.4 update to the iOS app added a number of small features and fixed a number of issues. The most noteworthy of the new features are both for Canon only and are a depth of field preview while within live view (a button will appear to the left of the capture button and is iPad only) as well as the ability to do HDR and intervalomter shots while in live view. A note of caution that keeping live view active can potentially cause some delays on things and in rare occasions issues, but it can be done. We do hope to be able to roll out the live view HDR/intervalometer feature to Nikon, but don't have any timeline at this point.
The most noteworthy issue that was fixed dealt with improper rotation of some NEF's when viewed as well as incorrect aspect ratio's of portrait images when saved with a watermark. I'll also take the time to note that saving to the iOS library does take longer with "Save with Watermarks" on, so if you are most concerned with speed, be sure to leave that off.