It already killed off Research in Motion (RIMM), but it continues to make even market leaders Microsoft, Amazon (AMZN) and Google feel grossly inadequate. They are constantly looking over their shoulders and trying to figure out what Apple has up its sleeve. The result is distracted rivals.
In this case, Apple is taking away every possible advantage it has presented Google and transferring them to Google's rivals - essentially playing "enemy of thy enemy."
The tension between the two has certainly reached an all-time high, and that has helped markets and the world in general enjoy some of the best innovative products known to man, many of which humanity now rely upon heavily as both have endeavored to provide consumers what they haven't realized that they need yet.
For this I can only exalt that "all is fair in hate and war." Hold your mail, I realize that's not how it goes, but there's never been any love lost between the two.