It's not a perfect solution, settings, files, or saved states are not preserved, and you will need to use the same Windows Live account as you had on the older phone, but it certainly reduces the workload and frustration.
Running the app gives you a checklist of all the applications that you have downloaded from the Windows Marketplace, including those you have downloaded and deleted from your phones. Run down the list, ticking and unticking the apps and games you want, and away you go.
How does it work? When you tap on the Connect button, Reinstaller prompts you to login to https://www.windowsphone.com and then scans the website for all the apps that you have ever installed on your Windows Phone. Once you are done with that, you can tap on the on the Install button on the main page. The install page displays list of all the apps that are associated with your Live account. Using the jump list and check boxes you can install all or some of them.
When you start the installation, Reinstaller invokes the Marketplace tasks for installing the apps one by one as that’s the only way to do it on the current Windows Phone release. Tap on the Yes button to start the installation, No to skip the specific app and Stop to prevent further prompts and come back to the main screen.
Hat tip to Mobility Digest for this one.