If you want to see how well you’re writing, the free text-analyzer Expresso will give you a detailed breakdown of whatever you give it.
The web-based Expresso, spotted on Product Hunt, allows you to type or paste in text to see different metrics of your writing. Hit the "Analyze text" button to see things like what percentage of sentences are extra-long or short, which words are filler and which verbs are weak. After clicking different metrics, Expresso will highlight the corresponding text with different colors.
Expresso, currently in beta, lets you closely examine how you write and how often you use certain types of words. By analyzing my own writing, I can see that I often use clustered nouns. What are clustered nouns? Expresso will tell you they are "three or more consecutive nouns." Hovering your cursor over any metric that you don't know will give you a concise explanation, so don't worry if you can't pick out a nominalization or modal on your own.
While Expresso gives you all these helpful extensive metrics, that's all it really does, so don't go uninstalling Microsoft Word. There are no options to format the text in any way or save it, so it's more of a handy tool that fits alongside a good text editor.
Expresso has an obvious appeal for writers, but it could also be a helpful for editors or teachers to quickly paste in text and catch weak parts that could be overlooked or get an idea for writers' different patterns.