This is not yet another drupal vs. wordpress topic I promise. But for a number of reasons I am considering moving a few of our more complex sites from drupal to wordpress. In large part this move is due to the complexity of full point version upgrades in drupal and the time, money and hair loss they often cause. A related thread on the drupal site from which I've yet to receive an answer is here: http://drupal.org/node/1854202 and the net has a good number of posts with related concerns.
Before you answer, please be someone who has kept a wordpress site completely up to date that has a fairly large and complex site (i.e. 100k+/month plus fair customization). Ideally, include a link to sites that exemplify this experience.
I would like to know how often wordpress and related plugins will break during the upgrade cycle. How often do you have to wait after an upgrade is released before the plugins catch up. I know full well that this can vary quite a bit depending on your site and plugins used, but there should still be some good experiences out there. Any habits to help avoid problems with updates..., etc.?
If you've used drupal and wordpress on fairly complex sites (community, ecommerce, multiple contributors, etc.) with decent traffic and can speak to the issues of keeping core and the plugins/modules up to date that would be great.