iMessage is yet another app/service combo that provides SMS-like message communication via TCP/IP instead of SMS.
3 reasons why iMessage won’t kill SMS — Mobile Technology News
This increases performance and lowers end-user cost.
Will it matter that Apple provides a solution, considering there must already be 100s (maybe 1000s) of apps that already do this for free?
The issue is of course that both parties need to have an app to be able to communicate, and due to that Apple has a bigger chance than many others to get people to use it, as such apps are not inter-compatible.