Deprecation of TOM API
The TOM API is deprecated in favor of the Core Service, introduced in SDL Tridion 2011.
Most calls to the TOM API typically occur in templating code and in event handling code, so migration normally consists of migrating your templates and your event handler code to TOM.NET. In all other contexts, the Core Service replaces the COM-based TOM API. If you currently call the TOM from any other code, replace such a call with a Core Service call.
For more information, refer to the API reference documentation for TOM.NET and the Core Service.
Also note that it is not possible to use data in .NET that was obtained using MS XML (which is the case when using the TOM API). Microsoft Knowledge Base article 815112 explains this issue: http://support.microsoft.com/default.aspx?kbid=815112