"The same argument applies here. Is it worth it to your average consumer to upgrade their system when, in all likelihood, they won’t notice any difference in the speed in which they can surf the web. If it takes Word 9 seconds to open instead of 11, was it worth the money?"
For me, it's more of the difference between that BMW starting every time and starting sometimes or stalling out while I'm driving. If they promise that, I'll pay the same as I paid for Leopard. If it's just a performance increase, I'd have to see it before I commit to any price.
Quality Doesn't Always Have Sex Appeal: How Much Should Apple Charge for Snow Leopard?