I've used this site on a number of occasions and have never had any issues. It is very user friendly, there are no additional fees to book flights, and they provide you with your bottom line price to include tax and fees upfront. You can choose from multiple airlines, and can easily see the difference in price between non-stop flights and those with stops to see if the savings are really worth the extra time. I like that you can also sort the flights by departure time or shortest flight so that you can chose the flight that best suits your needs.
Upon placing an order you can select which seats you want on the plane and then notate any special needs/requests you may have. Immediately upon placing your order you will receive an order confirmation via email. I've used them for booking flights, car rentals as well as hotels and I've never had any issues with my reservations, etc.
You will find their pricing to be better than most sites specifically on flights, so I would highly recommend checking out their site anytime you are looking to book an airline ticket. Though I had a great recent experience with www.lastminutetravel.com (feel free to read my review), ultimately when booking my ticket to Florida, www.cheaptickets.com was about $50 cheaper for the same exact flight, so obviously I booked my flight with them. :)