Jackalope and I played Pokemon Mystery Dungeon with a barcode controller we made from printed barcode text taped sloppily to a piece of paper and some human-unusable key bindings to a DS emulator.
This setup is with many, many disadvantages. Any game that requires sustained key holding to be playable is out. Any game with any timing requirement is out. Games with multiple simultaneous button presses are out, unless we create barcodes for every such button combination. Games that are just plain long and tedious by themselves are also out. And quite frankly, the barcode reader we use is terrible and has a success rate of about 50%.
On the other hand, this setup made diagonal movement much easier since we created distinct barcodes for diagonal input. This was particularly noteworthy in Mystery Dungeon, where diagonal movement is strategically noteworthy in contrast to the mediocre abilities of the DS to detect simultaneous button presses. Complicated button sequences could also be simplified by printing longer barcodes.