One thing that's become abundantly clear as we sprint toward launching TopNotchThemes: creating a theme that can be used for a variety of sites is a very different project compared to doing a theme for a particular site.

Designing for a single client has its own difficulties in the form of pixel perfection, changing designs, conflicting requirements, fluctuating budgets, and more. But you know what you're shooting for and you can pretty much tell when the theme for a site is done. It reproduces the design, delivers the functionality, and makes the client go "wow!"

When you're designing a theme for a client who could be anyone, however, there is so much more you have to take into account. Now add the incredible flexibility that Drupal provides to the end-user/site administrator, and the factors you have to take into account rapidly multiply. Sure, you can create a theme that has lots of flexibility in dimensions, layout, block placement, etc., but as your theming becomes more general, your theme can also start to look more generic. How do you allow maximum flexibility for the user of the theme, while still providing enough detail and specificity to give the site real personality?

The solution is to put yourself in the shoes of a wide variety of your end users. You have to empathize with an unseen person who has just activated your shiny new theme on their treasured site. What is the kind of person who buys this particular theme going to want to do with it? What is the tipping point when an abundance of configuration options becomes confusing complexity? How many different page layouts are they realistically going to use at once? Do you aim for plug-n-play functionality or do you buy some more power at the cost of introducing a learning curve? And when is the design done?

The answers are a little different for each theme, but as you produce more themes, you start to get a feel for your unseen end user. By realizing that they are a combination of what you are ("If I were using this theme, what would I want?") and what you are not ("What would someone who didn't have my preferences/biases want?"), you begin to find the rough limits between what will enhance a theme and what will just detract from it.

Sure, the answers to these questions start out fuzzy, but they ultimately get clear, because the whole issue is moot if you don't deliver a finished product ready for a live site. The empathizing phase eventually tapers off in favor of nailing down the details, testing for functionality, validity, accessibility, cross-browser usability (and a lot more), packaging it with documentation, and getting it on the online store shelf.