[T-R]

One of the nice benefits of writing for an old console like the NES is that emulators are often the first things ported to new platforms - you effectively get all the portability of writing for a virtual machine, along with the ease of running on only one type of hardware. Most of the hardware/compatibility concerns (Can I maintain a proper framerate on this hardware? Is the screen large enough? What kind of controller does the user have?) are on the person porting the emulator, not the developer. Also, for the user, this means any configuration only needs to be done once for all of the games on that platform.

As for hardware, if you can't find an NES, you can always use a third-party retro console, like the Retron 3.[1]

Also, if you're worried about compatibility, Byuu's cycle-accurate SNES emulator[2] has been expanded to run NES, Gameboy, and Gameboy Advance games, so testing on actual hardware is a lot less necessary than it used to be.

[1] http://www.thinkgeek.com/product/13f8/ [2] http://byuu.org/higan/