What still amazes me about WordPress is that the custom theme still works today. The markups had changed dramatically over the years from XHTML to HTML5, but the underneath structure remains the same. Another indisputable feature of WordPress is the one-click upgrade. My site has never been broken when I make the upgrade. I even tell all my clients with confidence to just click that button.
The downside of WordPress is that it takes a lot of work to build from scratch, especially if you don’t know exactly what functionalities will be used in the future. Take this site for example, I have no functionality for widgets because I don’t need them. My clients, however, would need those types of feature to be able to add extra things to their site.
A better approach would be to take pre-existing templates like The _s Theme, Toolbox or Twenty Eleven and customize them for your needs. The drawback is that you’re losing precise control of your markups and many functionalities that came with those themes you might not need. Working from complexity to simplicity is where WordPress is similar to Drupal. The different is that WordPress’s default markup doesn’t make Zeldman cries. In this regard, MODX shines because it gives you total freedom to write your markups.