Sorry about the slow review! But here it goes.. Just to clear up something that was mentioned above, the ski ( pictured above)that I skied was the shelf model that replaces this season's i.Sl, not the i.Sl RD. The difference between the two is that the Race Department ski is sandwich construction, w/ 90º sidewalls, while the regular shelf model (pictured above) is cap construction. I believe there is also a difference in the bases, and the RD ski is stiffer. I got two days on these bad boys, including a live race course with timing.
My initial impressions (freeskiing blue terrain):
When I first slapped on the skis they felt light on my feet and my first few runs they were fairly snappy. The conditions were soft granular, with an icy layer underneath. The dimensions allowed the Heads to initiate quickly, and the sweetspot was large and centered. I was impressed, however I had yet to ski them on anything firm.
Second Look (slalom course, hardpack/ice/softspots/ruts)
In the course, the skis were quick. The first thing I noticed was they were great at holding an edge, they were lively but dampened vibrations and ate ruts well.
I'd definitely say that the ski was very stable. The one thing I did notice was that the ski was a little softer than I would prefer. Just for reference, I'm 6ft tall and weigh about 185 lbs. I think I'd be more inclined to go for the RD version which is a little stiffer. After skiing the Heads I also had the opportunity to ski this years Atomic 11.12 in the same lenght (160cm) and the same race course. In comparison the Atomics were much snappier and had more energy, however were not quite as damp although the damping was still good because they were slightly stiffer.
The same weekend I also had the opportunity to take next years salomons (164 cm, off the shelf slalom ski) and rossignols (160 "worldcup" slalom ski, 90º sidewalls) for a couple of runs. In comparison, I like the rossignols for their increased stiffness and energy. Out of all 4 pairs, the salomons felt the most natural for me, and my style of skiing, and I had to make little to no effort to make em' rip, as soon as I pointed them, I felt like I was in the sweet spot for the rest of the run. But I also would be interested to try salomon's race stock ski for next season.
In conclusion, the Head ski was an excellent pair of slalom skis, and had all the characteristics I like in a slalom ski, however, I will definitely buy the RD ski if I choose to ski on Heads next season. Perhaps these skis would be an excellent choice for someone a little lighter, or lighter on their edges than I am, or someone who wont be crashing too many gates but still wants a quick turning, well damped slalom ski that has great edge hold.