It was only a matter of time before someone breached the void between computer and phone. Why did it take so long for someone (Apple) to introduce a desktop messaging system that inter operates with a phone.
That being said it's not perfect. Now and again it can lag when sending or receiving messages. The fix is simple if you experience this. If you installed Messages Beta, an early version of iMessage for the Mac that Apple released in February, uninstall it.
Somehow I missed the fact iMessage had been released officially it seems. Give it a try and let us know any feedback.