Themes are important part of any blog or any website we showcase. I do agree that quality of the content is the most important factor of any successful blog. But themes are the the outer package which attracts any visitor who peaks in to your site first. So its very important that you chose a right theme. You should choose a theme which interfaces your content to your readers. To accomplish it, your theme must match with the type of content you are posting. But setting up theme also somewhat time consuming and for most people its a biggest challenge. So most people once their theme is set never look back at them. What I have found out is that, many people are not aware that these themes can be quickly tried out before you go live on them. Basically you will be able to try out any number of themes in a matter of less than 10 clicks to visualize how your content looks and feels! If you know about it you may skip the further reading otherwise, I advise you to stick on to this article.
Hope this is of some help. Let me know if you have a question or some other suggestion which I am not aware yet.. WordPress has lots of hidden mysteries and we just have to uncover it.