One of the annoying foibles of Nokia's fledgling Ovi service was that you couldn't re-download your apps in the event that you lost your data. With the latest update, you can - but only on the device you originally bought it on.
On a recent Ovi blog posting, Nokia announced the update. In fact, it even goes as far as to place a video explaining the process of re-downloading apps.
It seems you have to be logged in with the same user name and on the same physical phone. If you have the mobile client installed, it'll need to be updated to version 1.5 (387).
What we want to know is: what happens if you lose your mobile?
We'd like to clarify one point. Redownloading is possible on a replacement device as long as it's the same model or a compatible one. You can check your device OS compatibility here: http://www.forum.nokia.com/devices/matrix_all_1.html