Two years. Thats how long the iPhone App Store has been around. That’s also how long it’s taken for Microsoft to launch their Windows Live Messenger application for the iPhone, available today.
In those same two years, dozens upon dozens of all-in-one IM service aggregation apps (Some of which, like Meebo, are free while others, like BeeJive, are not) have launched with Live Messenger support. If none of these previously existing apps satiate your hardcore Live Messenger needs, you can find Microsoft’s official offering here.