The main things to do in Vegas are drinking and gambling. If you're not much of a drinker or gambler, its not as much fun.
Vegas is a party city. Every hotel also has a club or lounge for those interested in nightlife. But, they aren't much different than the clubs you can find in most downtown areas, and they are overpriced.
As a non-smoker, the indoor smoking allowed in Vegas was frustrating. Nevada is one of the only states that still allows it, which is great if you're a smoker, but a shock if you are not.
Vegas is known for it's shopping. their are numerous high end luxury stores scattered around the strip, and a number of malls that cater to the middle class. It's great if you're a shopper, not so much if shopping isn't your thing.