yes have all heard of them and many have installed them. you can get them from many different sources, such as West Coast Classic Cougar, Classic Design Concepts, and many more.....
WebElectrics sells a set on Ebay for 69.95. They require cutting and splicing a few wires, but it is WAY easy. Their instructions are crystal clear. Took me about 10 minutes per side. I suggest using a butt splice connector and heat shrink tubing instead of the wire nuts provided with the kit, however.
I have them on my '96 Cobra for the last 4 years. They operate at the perfect speed and easy to hook up. Tim from www.ponyperformance.com is great to deal with.
Look into Meter4it.com. I think these look so much better than regular sequentials. It even gives you 3 choices, stock, sequential and the best, Chaser lights by just changing a jumper. I'm getting them for my '06.