Negatives organizes each of your friend's Instagram photos into a filmstrip of thumbnails. Your friends are grouped chronologically; the friend with the most recent post is listed at the top. You can swipe on each filmstrip to view a friend's photo thumbnails, while tapping on a thumbnail expands it. When viewing an expanded photo, you can swipe sideways to browse the previous or next photo in that feed's chronology. Tap on an expanded photo and you are presented with a three-by-three photo grid of larger thumbnails.
When viewing an expanded photo, the poster's comment (if there is one) sits above the photo, while the number of likes and comments is listed below. While you can see the number of likes a photo has garnered, you can see who has liked the photo. Similarly, you can read comments of a photo by tapping the comment icon but you can't add your own. Lastly, if you see a hashtag in a comment, you can tap on it to open a filmstrip of photos with that hashtag.
At the top of the app's home page is a search button, but the search functionality is very limited. It lets you search only for usernames and not by keyword or hashtag.
I don't think I'll use Negatives all that much on my iPhone because of the inability to comment or see who has liked a photo. (The inability to post photos to Instagram via Negatives is a given; no third-party app has this ability because of restrictions Instagram places on its API.) Negatives holds promise, however, as an Instagram viewer on the iPad since Instagram has yet to release a tablet app. Still, I'd like Negatives more on the iPad if it supported landscape mode.
Negatives is free so take it for a spin on your iPhone or iPad and tell me what you think in the comments below. And if you have a favorite Instagram iPad app, I would be curious to know what that is, too.