I have never booked a priceline or hotwire tickets because when I fly UA, I will want to make sure I earn my miles... and it counts to my status. Further, I had been decent in getting lowest fare options on my leisure travel with UA compared to other airlines anyway so why go to hotwire or priceline where I can dictate which airline I get to fly?!
As for hotel bookings with priceline or hotwire, I have been treated well by the hotel and had no issues.. sometimes got upgraded to better rooms. Nowadays, I book directly with hotel programs as earning hotel points and qualifying for hotel elite status became more relevent in my travel pattern. This meant more $ spent on bookings, but given liberty in choosing which hotel and which program for each stay.