A question was posted on a beta newsgroup recently asking for a demo of how to use the SSIS Rowcount component in a data flow. So, here's an example.
The only requirement is that you have a variable in which to store the rowcount. To run the package simply edit the "AdventureWorks" connection manager to point at your AdventureWorks database installation.
Note that the Rowcount component is a synchronous component and this coupled with the fact that it doesn't actually do anything particularly resource intensive means the performance degredation of your package should be negligible.
Very easy to do and very useful. I personally am using the Rowcount component to capture the number of inserts, updates and deletes done by each of my data-flows and then using the OnPostExecute event handler to put this information into a custom logging table. If you want more info on this, let me know.
As an aside, it is useful to use the Rowcount component as a destination during debugging when you don't actually want to place the rows that are flowing through your data-flow to a physical data sink.
-Jamie