I used MarketMuse a year ago to publish optimized content for my client's blog. It helps me find words and phrases related to my target keywords that I should mention in my posts. By adding these keywords, I can increase the chances of the content to rank for your keywords.

This is basically what SimilarContent can do you at a fraction of a price.

PROS:
- The Topic Difficulty feature is a great way to get an overview of a keyword's competitiveness/difficulty based on the ranking pages. I like how it also shows the different words used on the title and meta description ranking pages. You can then use them to optimize your content further .
- The Content Optimizer shows you what words and phrases you need to include in your article so you can optimize its score. You can edit the content in real-time to see the increase in your score
- Micro Niche is a great way to find questions that your audience is asking in your niche. You can export the question and run it using your favorite keyword tool to find questions you should optimize for. This is perfect for affiliate marketers and niche bloggers.

CONS
- No search volume for the Topic Difficulty. So you'll need a separate keyword tool to identify its search volume before running it using SimilarContent (of course you don't want to optimize for a keyword that people don't search for). I feel this is a missed opportunity for SC and would make the workflow and research process much easier for content creators
- You need to have your content ready when running the Content Optimizer. Else, it won't show the words/phrases that you need to include in your content
- No way to export the words/phrases to include in your article from the Content Optimizer
- Keyword Brainstorming and Today's Fresh Keywords feel useless to me. The former just shows you keyword suggestions based on your seed keyword. That's it. The latter is just keywords that SC got from Google Trends.

Didn't bother checking out Content Rewriter and I hope they abandon that feature since it's always better to let a human write the content for you.

Also, I'm overlooking at the cluttered UX/UI since I assume this isn't a very mature product just yet.

Overall, for what it's worth, SC is a promising tool as long as they refine the Topic Difficulty, Content Optimizer, and MicroNiche features. I hope they can add the search volume in the Topic Difficulty search as it should be a game-changer.