I've gotten a couple of questions on the SQL Server Central Management System (http://sqlcms.codeplex.com) that I blogged about yesterday. It's simply a methodology you can use to manage and monitor your SQL Servers using the tools you already have in SQL Server 2008, such as Policy Based Management, Central Management Server Registrations, PowerShell, the Management Data Warehouse and so on.
"Does this replace System Center Operations Manager / HP Openview / Our Current Monitoring System?" No. If you have one of those, you should definitely continue to use them - you're already satisfying the need of a central way to find, monitor and report on your systems. Those are also far simpler to set up and use - they come ready to work. The SQLCMS is something you build by hand.
You could, however, use some of the concepts from the SQLCMS in your environment. For instance, with a list of servers from SCOM or OpenView (I know, OpenView has a new name, but I just can't get used to it!), you could fill the SQL Server 2008 Central Management Servers feature to register them there. I show you how to do that in my example code in the project.
So the SQLCMS concept is just another tool in your toolbox. If you have a solution now or are looking at one, by all means use those. But if for budget reasons or simply because you like to build your own system, check out the SQLCMS project - use the comments there as well so that others can learn from your processes.