Two or so seasons ago the Eagles found themselves in a similar position against the Cowboys. Brian Westbrook cracked a huge run and was about to go into the endzone untouched, then he slid down at the 1. Ran the clock down, kicked the game winner, end of story. There was a lot of complaints in a similar fashion. "That is cheap" Yadda, yadda.
Often times it comes from people who don't have basic understanding of how the game actually works. Its one of the smartest moves in football when the score is within 3 points of a win or loss and there is still time on the clock. Well coached teams understand and will do that.
Bradshaw's problem was there simply wasn't enough room for them to do it. He was likely told to go down instead of scoring, but he still had to move forward, and they obviously weren't expecting the defense to just part like that. He didn't have enough time to properly react, or do what should've been done, and slide feet first (sliding feet first kills the play at the spot of the slide). It was good effort though, and led to a more exciting finish at least.
Good game overall. Excellent coaching on both teams, but with two crusty-ass old coaches like Coughlin and Bellichick. This Superbowl, however, did seem to lack that certain aura of excitement that has been around the past few.