I have spent a little more time playing with this tool, and actually I am liking it more and more. It fetches results without with color coding, and the interface is straight plain, but it runs circles around all of my other programs speed-wise. This thing is fast.
The most unique thing Serp Attacks has though is probably the PPC fetcher, it is more detailed than SEMrush, and very useful. If you collect the data over a period of time you should get some very interesting insight into your niche.
Now I would call it a must-have (it doesn't replace anything else, but add it to the list of software you want to have onhand)