Tennis videogames have been pretty complacent in recent history. The Virtua Tennis and Top Spin series seem to alternate release years, and every once in a while gamers will get a mascot-based variation starring Mario & Friends (or more recently, Sonic & Friends). The point is that neither Virtua Tennis nor Top Spin has been particularly inclined to change up their game in any significant way. It could certainly be argued that they don't really need to: The "hold shot button and get close to the ball" mechanic of both series seems to be quite popular and without any discernible major flaw.
That's apparently not good enough anymore for the Top Spin team. Top Spin 3 requires that you hold down your shot button, get close to the ball, and then release the button to swing. It's a small change on paper, but it'll definitely take some time to adjust to it, and it puts a renewed emphasis on speed, stamina, positioning, and timing. Whether or not this more accurately emulates the feel of real tennis remains to be seen, but at least it's something