Ham mode has nothing to do with the food. Go Ham in this instance means "Going hard as a motherf**ker!" Which means you want the script to go as fast as possible to collect as many hits as it can to fill up your queue. Great use for batches that drop during the day. It shouldn't be used for surveys or other hits that continuously drop for the whole day. It's best for those batches that you have no idea when they drop.
Instead of using the normal cycle timer it will use a new cycle timer for the ham mode which is set in the timers option menu. By default it's set at 700ms so it collects as fast as possible. Having a lower timer than the point where mturk sends pre's gives a really good chance at getting hits in a batch before other people. There is a slight delay to mturk's PRE response so there are a few seconds that pre's won't be sent. The script actually has a different counter when getting pre's in ham mode so you can compare the pre's you get normally to the pre's you get in ham mode. PRE's in ham mode is expected so don't be surprised.
A big thing to remember here is that a panda will always get a hit first before it even reaches the search page. For example some batches drop at unknown times. If you find out a batch has dropped by having a panda on or another script alerted you to it then you can instantly push the GoHam button to grab as many hits as possible before it gets to the search page where others who are not running a panda will find it. This could give you many seconds or a minute jump on them before competing with everyone else. Remember Ham Mode will stay on until you turn it off so make sure you turn it off if you have other pandas you are waiting for especially when you have a full queue.