Had an awesome morning on this beast, the wind built to 11-13 knots according to the local airport, I rigged the 17 Speed and the old 137 Wave Tray down at the local beach.
Flysurfer give the 17 a range of 7-17 knots "for a very good 75 kg Rider"
www.skywalk.org/
At 11 knots I was fully powered. Heaps of boardspeed and amazing upwind. Turning takes a while, not quite like steering a barge, and better than the 17m Psycho2, but slow especially compared to Speed 10.
There are some pics around of Armin from Flysurfer paragliding under a 17 Speed. Kiting with it is a bit similar, floaty! I was jumping transitions, not always intentionally, and just kept flying along a metre or so high, a fun way to lose some of that ground you get by pointing so far upwind.
I've had a few sessions so far, on the beach in 5 knots, it will actually fly in 5, trying to surf in 8-9 knots, I'm pretty sure I'll need a big flat board for this, and another session like this morning in about 10-12.
The accepted wisdom is that 17m Speed is comparable to a 25m LEI. I've never flown a tube that big, had a go on a 20, so I can't really make a foils vs tubes comparison, but a few things are obviously better about the speed. Not pumping up for starters! Safety is good, though rest pull is a concern with a kite this big. I landed solo on the safety when the wind picked up today with no probs, flagging the kite out once on the beach by pulling in one of the steering lines. Relaunch is great, as usual with Flysurfer kites, because you can launch in reverse. In the very bottom of the 17's windrange I've heard relaunch can be difficult but then again, what kite is easy to relaunch in 7 knots?
I'm working on a plywood copy of the Spleene Session 141 as a lightwind board so hopefully I'll be able to get a bit more on the low end.

To add to puppets thread "you know you're addicted when" you buy the most powerful kite in the world so you'll be able to kite even if it's only blowing 8 knots.