Many people have felt a great deal of anger toward Nintendo after the release of the DSi and its subsequent upgrade (XL) because of the lack of the ability to transfer downloaded software to another system, even with the SD card slot available for use. Well, no more sad faces, according to a hardware fact sheet (PDF,Japanese) it appears that it will soon be possible to transfer your Mario clock to your newly purchased XL or replacement DSi, this also means that you can do the same when the 3DS is released. It is not mentioned whether you can transfer from a DSi to a 3DS.
Some (unspecified) software can’t be moved, and Nintendo warns that there are limits on the number of times a transfer can be undertaken, but this is leaps and bounds ahead of the DSi’s current limits, which are set at zero games and zero times.