Honestly there is only one negative in losing Rudy Gay. Sending out Gay for Tayshaun Prince and Austin Daye may be a huge positive for floor spacing and three shooting, two things Memphis has struggled with the last two seasons. But now you have to wonder who gets the last shot at the end of games. Most recently, Gay hit a go-ahead bucket to defeat the Philadelphia 76ers, but now that job will most likely go to either Marc Gasol or Zach Randolph.
Several times Gay has come up big for this team at the end of games. The game-winner over Lebron James and the Miami Heat, the Philly shot, the three to go into overtime against the Phoenix Suns and Toronto Raptors, over Kevin Durant to win the game and a few others. If the "clutch gene" exists, then Gay has shown that he possesses it. While he is no KD, Lebron, Carmleo or a Paul Pierce, he belongs in the second tier of small forwards (Nic Batum, Paul George, Luol Deng). At times he lacked effort, but when Gay came to play he was a solid player.
Some other things that can be looked upon as a negative could be losing the team's only "flashy" player. Since he's entered the league, Gay has filled the Forum with a lot of exciting dunks on and around players. Chemistry may be another issue as this has been the primary core for the past 4 seasons. They know each other, where each other wants to be and what everyone is capable offensively. It'll take some time Prince to get accustomed to the offense and there is a chance that that time is the difference between the third seed in the Western Conference and the 5th seed.
The overall outlook on the trade is completely positive. With time these negatives can get the kinks worked out of them, but these are issues that should have an eye kept out on them.