Yesterday Microsoft announced the release of the Load Testing Feature Pack. This gives Visual Studio Ultimate with MSDN users the ability to do unlimited load testing.
Before you had to buy separate Load Test Packs. This has now all been included into Ultimate Edition (including the load agent software necessary to run a distributed load test simulation), enabling you to load test with as many virtual users as you want.
Thank you Microsoft!
For more information regarding this new Visual Studio 2010 Ultimate with MSDN benefit, visit the Visual Studio Load Test Virtual User Pack 2010 page.