Lately, there has been a hurried slew of queries on migrating test cases to VSTS 2010 from other sources. The most popular q of course is to move test cases from Excel to VSTS 2010.

We have this facility to import work items from Excel to VSTS, right? Well, test cases are yet another kind of work items. So, you can leverage this feature to import your stuff from Excel to VSTS. You'll need to map your columns in Excel to the right test case fields though (and this can be a pain to do manually) However, test cases in 2010 have this field called "Test Steps" that are actually XML fields. The content in this is represented as an XML blob. So, when you export a test case from the 2010 server to any Excel worksheet using the regular Excel integration, you see this field containing some unformatted steps. So, if you have your test steps typically written in multiple rows in Excel, it becomes conversely hard to import those into VSTS 2010.
To solve this problem plus give users greater flexibility over what and how to import, we wrote an internal tool that lets you do mapping from Excel columns to test case fields via a small UI. It can also automatically pick up test steps from multiple rows and import them properly into VSTS without all the formatting hassle. This is still work-in-progress however and we don't have it available externally yet. I know a couple of our customers that just used the TCM Object model and whipped up a migration tool of their own. I believe we should shortly have *something* out to help folks that want to migrate - either a solution from our partners in the community or a tool on codeplex.

Once there is a tool to do this, migration from other sources should not be a problem. All you need to do is export from old TCM to Excel and then to VSTS 2010. [Edited to add - here is the tool: ]