I've used Gametime, Tickpick, and Vivid Seats. Never had any issues with them. Gametime claims you can score a great deal by waiting until the last minute. The first time I used them was for a Guns n Roses concert in Hershey. I didn't buy the tickets until about 10 in the morning the day of the concert. I got row 17 dead center for $80. I've never had luck with prices dropping like that for football games though.