I chose Drupal over Wordpress for its functionality and used it to develop a webpage (visible in its nascent form at http://chriswalkerimages.com).
As you can see, the website is unusably slow, both on the production server (GoDaddy shared "deluxe" linux) and localhost (XAMPP, Windows 7, x64, no performance issues).
I am using page caching for anonymous users as well as browser caching, so while the first page request takes > 30 seconds frequently, subsequent requests are completed in an almost-reasonable timeframe. Of course, this does not help load times for registered users.
During development with the Zen theme, I thought the slow speeds were due to the theme registry being rebuilt on every page load. This is not the case: theme registry rebuilding has been disabled in every possibly related .conf file and double-checked in the MySQL tables.
I enabled Xdebug on my localhost and examined the results using kcachegrind: it appears that almost all of the loading time is repeatably due to these php functions:
drupal_load and system_list call drupal_get_filename (~58 times combined).
drupal_get_filename calls drupal_system_listing (~16 times).
drupal_system_listing calls file_scan_directory (~32 times).
Most of the time is spent in file_scan_directory, which is called (including self-calls) ~1184 times.