I disagree with Marzocchi damping as the best. I really like Answer's TPC+ and they are the company building the SPV setup. While Marzocchi has the HSCV (High Speed Compression Valving), I have never really been impressed with any Marzocchi SC forks I have ever ridden (Z1 FR, EXR, and a few of the DJ's). Manitou has a much more plush and progressive style.
I think most of the above shocks are not focus built. Rather they are blanket shocks.
They all do nearly the same thing, and can be used in any application (I've seen 5th's on DH bikes and XC bikes). The only semi-purpose built shock I listed was the Avalanche. Every other shock listed is used in both worlds of XC AND DH that I have seen.
I stand that Marzoochi is a day late and a dollar short in the rear shock. I doubt they will offer anything new, and I doubt that they will do anything significantly better. If they are better than the Vanilla RC, then that's cool, but the 04 Vanilla's are SPV and they fixed the rebound blowing problem (supposedly). So they have a pretty lofty bar to clear. It will either make everything cheeper for competition, or will be cheap just to sell without affecting other prices.