Rocks! That's all I can say.
My friend bought a Mortal Kombat arcade a few years back and set it up for MAME, which allowed him to play thousands of old arcade games on one machine. He eventually sold it before I could buy it from him. I've been wanting one ever since.
Well, I got one! Sort of. I got all the MAME roms, and the MAME32 Emulator program for windows, but playing with the gamepad just wasn't the same. So last nigh, I went out and got one of THESE!
The X-Arcade 2 Player Classic Arcade Console

This thing is JUST like the arcades.
Now I have over 2000 arcade games to play, along with my NES and SNES roms (which work great with this controller, hehe). Imagine playing Zelda or Metroid on an arcade machine. What a feel!
By the way, it hooks up as a keyboard, not a game controller, and it has 3 programmable modes. This thing ROCKS! I have it hooked to my laptop in the living room, and my kids and wife LOVE it!
Ratings:
MAME32 and Roms - 10 of 10 (actually closer to 20 of 10

Cost: Hmmmmm

X-Arcade Dual Player Controller - 10 of 10 (equally as pleased as with the MAME32)
Cost: $149.99 plus tax.
Value/Satisfaction rating: Sorry, I can't count that high....