It's been over 10 months now that I'm using Serpstat and I'm convinced that it's one of the best rank tracking solutions on the market as of to date. With that said, I must admit I hadn't switched from other tools completely.
The tool offers a deeper search and pulls through local SEO results much better that any other tool. Which means that with other rank tracking tools you'll have to manually research SEO local results.
The other and perhaps the most important feature is it's unique ability to show not just your rankings in SERPs but all top 100 SERPs for tracked keywords the ability to add competitors straight to your project. This means that you don't have to create separate projects to monitor your competitors.
Another plus side is that it's very user-friendly and well-designed. I was intuitively easy to switch to it, especially if you have experience with tools like SEMRush or Ahrefs.
The downside is that it's relatively new tool and it still lacks few odds and ends to win SEO/PPC specialist completely. For example, I would be delighted to see German, French, Spanish local Google dbs.
I actually asked them this very question and they told me that it's high on their priority list along with new cluster research feature.
Well, I'm all waiting;)