Hi Scott,
So far just one dongle. I keep saying that I am going to build my backup dongle but so far its just talk. To be honest I think a backup unit is a good idea. Here is my reason, While the show is going and you are working on a spare controller there is no way to test it. Now for me I like to write hobby program once in a while where a spare would be very useful. Now next year with the SS I can see for myself a big need for a backup since I won't be able to use the main dongle once it setup for pixelnet (of course I could reprogram the pic but..)
Sorry for going on so long
Cheers
Rick R.