How important are Meta Descriptions?

There have been numerous tests plus google stating that meta descriptions are not a ranking factor so the short answer to your question is no. 

However, this does not mean its not a great idea to include and improve your meta descriptions. Google will often use this tag to show in google search. Having a great meta description can drastically increase your clicks so, in turn, improve the number of visits to your site. 

We often see though this tag overdone and ends up being a sales pitch, google will often ignore these and pick something from the page itself.

You should attempt to accurately describe your page with an enticing description to get the users to click your link instead of your competitors. 

Agreed - short answer no.

This is an indirect factor. It can effect things that do ultimately effect your rankings.

The advice is to think about the users and provide a useful description to your page - if you do good, they will click through and this will help. If you have a good site and they stick around, this will help even more.

Meta description tags, while not important to search engine rankings, are extremely important in gaining user click through from search engine result pages. 

Meta descriptions play a big role in search results. In case you’re unfamiliar with the term, a meta description is the snippet of information below the link of a search result. In essence, the description tag is a short paragraph that describes accurately and succinctly so that the users and Googlebot can understand what the content of the web page is about.It’s purpose is to describe the contents of the page to the searcher.