There are a lot of questions out there about WordPress themes, what they are and why it is important to choose a certain one. Then…there are some clients that do not even know what a “theme” is and could care less. They just want a site up and running.
There are several free themes for WordPress.org and visually they are okay, I guess. Okay. I loathe them and refuse to work with them. They are a designers nightmare and are so restrictive.
I use Thesis and StudioPress (Genesis Framework) and here are the reasons why.

Thesis
Over a year ago when I first started doing web and blog design, I worked primarily with the Thesis theme. Loved it. Thesis is very user friendly and as a new designer trying to figure out WordPress and learning all about the wonderful world of coding, it was a great starting theme for me.
It is a perfect fit for the businesses who just need a no nonsense site up and running. If they need to just change the background because they have a new logo, just click a color and save. Many of the bloggers I work with use it as well because it allows them to get into their site without feeling like they are going to mess it up. They can make simple edits to the visual of their site and it is all laid out simply on the screen for the user.
One of the main negatives for the basic user is the need to access FTP files. A real bummer if you want to add, let’s say, your own header. But a minor tackle and you are on your way.
Thesis. Good theme. Used it often for people.

StudioPress (Genesis Framework)
StudioPress came into my design life early but it was just changing things to a live site. Then as I took the plunge into learning more about coding and taking my abilities to the next level, I looked at StudioPress more. Each theme is crisp and so professional looking. It takes your site to the next level visually and “under the hood.”
It is now my recommendation and go to theme for clients. I will lead a client towards these themes over Thesis any day of the week. The fact that the online “A-Listers” like Chris Brogan and Darren Rowse use StudioPress should also give you a second look.
Whether you are a church, photographer, business, or a mommy blogger, Studiopress has a theme that is custom for you. I not only really like the variety of themes that they offer, but I appreciate the fact that they are not limited and created by one person. Having so many contributors for the theme designs, every site looks unique. Jula Studio was designed with the Enterprise Theme.
But why listen to me? Go check them out for yourself!
So there it is. My two cents. Have more questions? Feel free to email me and I will answer any you have.