Not better than Netflix. Actually I have both, and the only time I've used Prime's instant video service is when my wife is using Netflix upstairs. The real value of Prime is still the free 2-day shipping. If you have a Kindle Fire, I suppose the video service would be a little more useful, and the lending library is a pretty sweet idea too (one I wish they'd unbundle from the Kindle to be honest).
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"Take the cheese to sickbay!"