This really is one of those things you do just so you can say you did it. The ride is pretty brief and pricey for such a short ride. It's $16 for each person, or $64 if you want a private 2 person ride.
We did the outside ride during the day. The gondolier sang and was nice. We rode with 2 strangers, which was kind of weird and not really that romantic. You're wondering if they are looking at you, you're looking at them to see if they are looking at you wondering if you are looking at them...But it's still cool.
Time saving tip: You can make same day reservations so you don't have to stand around waiting.
I much preferred the San Diego Gondola Company ride: http://www.yelp.com/biz/the-gondola-company-coronado#hrid:WC8X2UT5o-H30ibzCZa75Q/src:self
But while in Rome, errr..Vegas...