Carousel - $1.99

Carousel is a stand alone Mac app for all you Instagram lovers out there. Upon launching the app you instantly get an elegant twitter-esque feel with it's scrolling timeline. Complete with built in shortcuts you can view the images larger, comment and of course heart them right there in the timeline. Sorry, there isn't an upload option, but then again it's supposed to be a mobile app anyway, right? In addition you can also view other users who liked the image as well as seamlessly view their timeline. I can already hear you, do I really need another IG viewer, and why would I want to pay for a viewer when there are websites out there that let me view for free?
Remember how I told you Carousel has a scrolling timeline, well it also has notifications letting you know when new images have arrived in your feed. Let me take that one step further. Let's say you haven't opened Instagram in awhile and you're trying to get caught up on all the goodness in your timeline only to find out IG won't let you load anymore images. As long as you have Carousel open in the background it's continually updating all your new posts while still sitting on the last post you viewed, all you have to do is scroll up. 
Carousel is a great minimal app for your mac that gets the job done.
Here is a free 15 day trial: www.carousel.mobileux.com