Typemock has released Isolator v7, and this is pretty much the release you've been waiting for.
Let's ignore the visual test coverage, the test autocompletion, or even the automated test runner that runs your tests in the background so you instantly know when you write something that breaks a test. That stuff all rocks and you'll love it.
This is the version that lets you run tests against different versions of Isolator without having to uninstall/reinstall different versions. A long-running issue, you've previously always had to build your tests and run your tests against the exact same version of Isolator. Not a huge deal if it was a product you could check in alongside your code... but you have to install it and you can only have one version installed at a time. No longer! They've finally fixed my #1 complaint and I am stoked.
Oh, and they added mocking for the filesystem (System.IO.File) and environment (System.Environment). Nice.
Go check it out.