Anytime I'm on vacation in another city, I try and do these sightseeing tours. I believe it's a good way to see what your city has to offer, especially if it's your first time or you're not familiar with the city. On my second to last day, I decided to look on Groupon and look for activities and they had a voucher for various options for the tour. I opted for the one day hop on, hop off for two ($40). They had additional options which included an extra day with lunch or a ticket to CSI experience.
There was a bus stop not too far from the hotel and we took the one hour ride from the strip through out Vegas, got some knowledge of Vegas, saw some greats sights, and some not so great sights in the Downtown part of Vegas which appeared to be a bit sketchy.
I would say it's definitely a good idea if you're a first timer in Vegas like myself and hop on and hop off and see the town!
P.S. Don't forget to tip the drivers!