I used that web site to purchase our tickets for our trip in May. I found great fares there. I understand it is owned by major airlines, too. The only problem is you can only get 4 tickets at one time. We had 5 in our family, so I purchased four, and then immediately went and tried to get the fifth on the same flight, it said it was not available. I almost died! I called the 1-800 number and told the person our problem and she was willing to do a one time refund; first she tried to get that one ticket on her end and she was lucky and got the fifth ticket. Using the site for the first time, they waived that extra cost for buying the tickets (I believe it was $5-10/ticket).
I then called the airline and made arrangements for all our seats to be together. We were on the manifest and we had no problems checking in for our trip or getting us together for the flights.
I would use them again if I found good prices.