I used Travelocity to purchase tickets for family members for a reunion I put together in 2001. I actually prefer them over Expedia, because for some reason, Travelocity does not make you purchase paper tickets. At the time, Expedia made you purchase paper tickets if you were not the one flying. Everything went off without a hitch and I purchased tickets online from both Travelocity and Expedia, along with phone orders directly to Delta and ATA.
Normally, I call the airline and purchase tickets over the phone. I can then check my itinerary thru their website or they will send me an email. I like doing it over the phone because if the price goes down, I can call and they will give me a credit without a hassle. It is my understanding, so I could be wrong, that if I purchase the tickets over the internet and the price drops, I do not get a "voucher" to use on my next flight. The same thing applies with Travelocity and Expedia, if the price goes down, they will not give you back the difference.