Activity requirements
You have to be physically able to get into most commercial helicopters and then be comfortable to sit in a very confined space while rocking around just a little bit.

Cost
You have to have a lot of money for fully charter a helicopter, but there are other options such as riding in a group with others. Many major cities offer helicopter tours for tourists as it's great way to see a city.

What Fiked recommends
If you're going to be using a helicopter as a way of getting from A to B, then it's a really good option as you travel at speeds of around 200 MPH and there's certainly an element of style to it. Helicopter tours are just as good, but can still be pretty expensive - there's usually more then 1 tour company in a city, so shop around. If you get motion sickness, try and get a window seat and take tablets to help you. The ride of a helicopter is actually really smooth these days, it's just a little unusual at first.

Best time to do this
I personally like to see a city by air at dawn or dusk to see the lights of the city as well, and clear weather conditions are a must. Cities where it's always hot like Vegas offer great all year round tours so you're pretty safe to book there.