SemRush is an advanced Search Engine Marketing Research tool, which is what the SEMR stands for. This is indeed the subject that that SemRush was best suited for. Recently however they addeded some features that are still marked as Beta, but which work pretty well, and really add a lot of value, making it a full SEO Analysis service. The 2 added features are the Rankt racking Service and the Site Audit feature (just released March 27th!), which is great for checking out on-site SEO, more on that later.
Basically all you do is to start from the big search box at the top of the window, where you can type in either a URL, Keyword or Phrase. Depending on what you looked for, a result page is shown, with many graphs and tables, mostly allowing you to drill down on the results. Especially keyword research and competitor analysis is very detailed, pretty much to the same level as Market Samurai, though both tools have their specific pro's and con's (so I often use both).
As an example for keyword analysis, simply type in joomla seo in the search box. You will also notice that the searchbox allows for localized results for many countries (not all, so check). This allows me to search locally, like here for the Netherlands:
This opens a screen with a lot information, like a phrase match report, related keywords, search volume, competitors, etc. At first the information seems a bit overwhelming and unstructered, so it takes a bit of getting used too. Happily they have a Youtube channel that offers tutorials to help yout on this. There is especially a lot of information about AdWords and AdSense information available.
If you type in a URL in the searchbox, you have acces to the Competitor information under the Organic Search options. This provides excellent information about stuff like competition level, number of commen keywords, etc.:
Drilling down on these results, using the SE Keywords button provides further information about this specific competitor. Especially this bit of information can be extremely usefull to see what they are ranking for. If you click the Common keywords you can even get a side-by-side comparison with your own site!
There is too much to tell about to be checked out. Further features are Backlink checking, Adsense and Advertising information, etc. What I want to show you next are the tools, especially the Position Tracking and the Site Audit tool:
I love to track my positions if I am working on a project, and this is the nicest tool that offers this I think, also because it updates on a daily basis. You enter a campaign for a site, tell the tool which keywords need to be tracked, for which region / country, and also you can track competitors. The tool also connects to your Google Analaytics and Webmaster account. The result is a nice overview of increasing and decreasing rankings:
Drilling down then tells you your exact rankings, plus the ones for your competition, and all on a daily basis.
A tool that has become available only March 27th 2014 is the site audit tool. This addition makes SemRush a very complete tool, allowing me to perform most of my tasks, as far as they can be automated of course. The site audits can either be performed as a single audit, or scheduled on a weekly basis. Once issued the audit takes a few minutes to end, resulting in a report with an overview that also allows you to click on any detail to find more details:
You can drill down on any issue, but also you can request all issues per URL.
So, all together SemRush could be a very nice addition to your toolkit. Play around with the free version, and sign up if you feel it's any use to you: