I do love the Famicom, but the original Famicom system pretty much sucks. There are converters out there, but some aren't as easy to use or as user-friendly. Especially if you're using a Toaster model.
This device allows you to play Famicom games and use the RAM adapter for Famicom Disk System a lot easier (and often cheaper) than most other products out there with the same function.