I just traded away the ailing T-Mac for Calderon and think it was one of the best trades I've done all year. Calderon is a true point guard. He has great percentages, nails a few threes, and bring in good assist numbers. Even a few steals too. All while keeping the critical turnovers low.
Kidd is more versatile. I don't see him "changing his game" or improving it any more than what you see right now. I thought about trading for him earlier when he was offered to me. But my team has a few SG/SF type players that are very versatile. I want my PG to be a point guard. T. J. Ford isn't gonna steal more than 10 minutes a game from Calderon... Only give him breathers. That's assuming he comes back at some point.