Well now that surely depends on several factors.

Firstly, a tripod renders any sort of image stabilisation pretty meaningless.
Then there are monopods, beanbags, clamps, suction cups and numerous other means of camera support which can circumvent the need for stabilisation.
Finally, many individuals can handhold such a lens perfectly happily at sensible speeds.

"Almost essential"? No, I don't think so. "Potentially extremely useful" would seem to hit the mark more closely, and I say that as a great fan of the freedom that image stabilisation gives.