Rick, that looks like a pretty solid lens to me. I especially like the fact that the lens retains its length and f-Stop while changing the Zoom due to internal elements moving instead of end elements. I like the water/dust-proofing also - big plus on a long lens with more elements to fog up.
I like the comments by Salvuccim about IS
and telephoto action
shots. In the past I never needed 'image stabilization' even up to 300mm since I tended to use higher film speeds.
Shooting Hydros with a Sony DSLR this summer I found that the shots taken with IS were just as much a gamble on blur as those taken without it. The clearest shots came simply from high speeds (set manually) where I'd allowed the f-stop to be automatic and manually set the focus at infinity (using duct tape
because the very-loose focus mechanism could easily go beyond infinity). With a sufficiently high f-Stop and a lens locked at (or just under) infinity it's easy to take shots at a variety of distances with no worry over focus. Still, auto-focus when shooting the typical skier drawing gradually
closer will probably be fast enough to make a difference.
For skiing I'd agree that even in night skiing (with enough lights) 4.0 is probably an OK f-Stop to work from if the ISO is set high enough.
Be sure to get a UV or clear 'filter' for the front of the lens as this is a great way to protect the end glass from scratches. If the filter
gets scratched up, you can just replace it.