iEDGE booted up great on my son's DSi XL...
He only uses the DSi XL to play games and watch movies, but other than not being able to get the soft-reset function to work from Moonshell 2.10, not being able to control the DSi XL's brightness from Moonshell 2.10, and a couple of games that lock up (the same games lock up a DS Lite and the soft-reset/Moonshell issue is there on the DS Lite, too), the card works great...
If you plan on doing other things (homebrew, wifi, etc), I don't know first hand...
The iEDGE cart even came bootstrapped to the appropriate firmware revision (Sudoku icon) from the seller, and works great with a 16GB SDHC card on both the DS Lite and DSi XL (although you're limited to 127 games per folder)...