I'm quite into speed... I bought a GPS back in about 1995 and hit 60mph for the first time in Vail over quite bumpy ground - and that GPS (Gamin 12XL) didn't record max speed, so I had to read it while going along, which was a bit of a nighmare. Since then I've upgraded to Garmin foretrex, which is a whole load better, and I also ski with an iPhone now too for corroboration (though its GPS is nowhere near as good as the garmin and often loses the track).
The Ice Flyer run in Engelberg is fairly steep and often empty, though has a poor runout, but I've skiied that at over 120km/h several times, reproducibly, which is a shade under 80mph. Weirdly, my fastest run was on a pair of 163 Stockli slalom skis :)
Now I live near Megeve and often get to ski long, open, completely empty runs first thing in the morning. Got myself a nice solid pair of Atomic SG skis and they just don't work great below 60mph :)
I was very curious about the iffy reputation of GPS speed readings, so I did a speed skiing day in Flaine where I could try out some DH skis on a run with proper TAG timing gear. I'd just got my ContourHD helmet camera too, so here's a little compilation of the day. The slope wasn't up to much and conditions were not good, so fear wasn't a factor at all and made it much more about how much speed you could get out of the hill (98kmh in my case). Over about 8 runs, my GPS was within +/- 2km/h of the timing gear on every run except one, where it was over by 22.
I got a nice clip from a day in Chamonix - 72mph on my old Volant Chubbs!
I often ski with my 6-year-old daughter too, and I've been alongside her at a sustained, steady 40mph, which I was quite shocked by! She wasn't that impressed.
Next season I'm planning to try and make one of the "pop KL" events, probably in Verbier which is ony a couple of hours away, see if I can hit my 100mph ambition...