The omega theme is pretty 'fat'. Currently its probably the biggest theme on drupal.org. You can do anything and everything in the GUI. You can completely customize the layout, turn responsive design on/off...I could go on for awhile.
My question is, do all of the extra settings eat up server resource to serve a page to the client? If I have a website that receive 100,000+ page visits a day, should I use omega, or create my own theme?