Drupal's Mutlisite feature sounds like the Holy Grail for whenever you want to run multiple Drupal sites. However, the answer to "Should I use Multisites?" is best discovered by knowing what Multisites is and how it might benefit or hinder your objectives.
In this video, I provide an overview of Multisites vs. Multiple Sites, and hopefully, the insight necessary to decide.
The later part of the video runs through an optimized setup for using/running Drupal's multisites feature. It showcases an Apache configuration for better security (blocking more files), faster performance (fewer disk hits) and easier upgrading (a better way to update than using site maintence mode).
One thing I forgot to mention, in the video, with using Mulitsites was the way to implement cron.php. Assuming you have shell access, you can easily use a script to do this. For my particular multisite setup, I use a cron shell script and special thanks go to user gnat and the others in that thread for their work!
If you're looking for more information about using multisites then head on over to groups.drupal.org.