The Freemont Street Experience should really be called the Freakmont Street Experience, ha! I've been here plenty but recently played tourist with (visiting from out of state) mother.
So the actual "experience" is over the street, look up every hour for a light show! I think that the Slotzilla zipliners give it a nice touch as well. But to me, there's more than that to the experience. You get to see a bit of the older hotels downtown along with their history and their lights. You could actually host a scavenger hunt finding the neon figures. In addition, you could host a scavenger hunt finding the most bizarre street preformers, ha!
There is drinking up and down the "experience" so feel free to duck into a casino and grab some booze to enjoy... chances are, most everyone around you is drunk. You can also stop and display your drunk dance moves in front of one of the two (or maybe three?) stages along the way.
If you've got the time and you're debating on visiting Freemont Street... just do it.