There have been several updates to Drupal core since the first of the year. I did a round of maintenance for my sites in February, but I’d skipped Drupal 7.21 since it was not a security update. Then, on April 3, 7.22 was released. Like 7.21, it’s not a security release but I thought I ought to upgrade. I ssh’d to my hosting service, and in turn, backed up each site, switched to maintenance mode, and did the module+core+database update with drush. Ran like a champ. I’ve only been doing Drupal for a couple of years, and I didn’t use drush at first. In fact, I only started using it when the web-based updates started throwing PHP errors on one of my sites. I’m happy I installed and started using drush, ’cause it sure does make maintenance easier.