The Views Bulk Operations module (a.k.a. VBO), is a godsend for busy Drupal site administrators. Don't just take my word for it - Lullabot wrote a chapter about it in O'Reilly's Using Drupal, it's included in the Open Atrium Drupal distribution, and it's even used on Drupal.org! Out of the box, VBO does a lot to streamline the things you do everyday, so that you spend less time doing them. A perfect example is bulk content moderation - with a few clicks of the mouse, you can mark a huge amount of comments as spam. You can even enable batch processing with a single click of a mouse so that you can literally do thousands of these without timing out.
VBO was attractive enough that we decided to offload the bulk/batch operations of Node Gallery to VBO. Integration for the most part was surprisingly easy - VBO "speaks" in Drupal Actions, so by writing actions, we were writing integration with VBO.
There's one undocumented case where VBO can be used that was critical for us. Most VBO actions you will find perform one action to a set of nodes, one at a time. Often times, that one action is to set a value of some sort on said nodes. In the case of Node Gallery, we wanted to be able to assign different weight values (used for sorting) to a bunch of nodes. The key here is that we aren't assigning a value of '2' to all selected node's weight, we want to assign a weight of 2 to node #1, 3 to node #2, 8 to node #3, and so on. While not straightforward, it's definitely achievable.
