Thank you for posting this. If anyone has other methods then please post here as well!
Viewing post in Unity Guide: Upscaling Your Low-Rez Game
Another method that would look sharper would be a pixel filter on the camera. There are some on the asset store for cheap or you could write your own relatively easily. Here's one I found. https://www.assetstore.unity3d.com/en/#!/content/85326. Not what I did mind you but it would make things easier for some.
Here is a free one I found. https://www.assetstore.unity3d.com/en/#!/content/16314