If you want to completely throw out search engine crawlers viewing your content, 508 compliance, and 5-10% of your visitors with Javascript disabled, then sure ignore Gracefully Degradation. Not to mention that Graceful Degradation is frowned upon to begin with, you should be Progressively Enhancing. Starting with a site deeply entrenched in spaghetti Javascript code and trying to make it work without it takes a ridiculous amount of time compared to just building the site without a single line of Javascript written to begin with, and just provide all the fancy features after you have a full, working site.
It may sounds harsh but most sites couldn't care less about accessibility because it's not required by law and because users with assistive devices don't account for a measurable portion of their revenue.
5-10% of your visitors with Javascript disabled
Not sure what kind of site you have there, my reports are more inline with what yahoo measures (i.e. hovering around 1%):
Starting with a site deeply entrenched in spaghetti Javascript code and trying to make it work without it takes a ridiculous amount of time compared to just building the site without a single line of Javascript written to begin with
508 Compliance might be a luxury in the US, but not making a website accessible would be a breach of the Disability Discrimination Act (DDA) in the UK.
I'm not aware of anyone attempting to enforce this however.
I think you're talking past each other. If you want to build a web-based spreadsheet application, you neither "progressively enhance" nor do you "gracefully degrade". Your browser is either a supported runtime or it's not.
Sure, if you're building a content site, you will want to have progressive enhancement, but if you're building a client-side application, SEO concerns and the other concerns of content-delivery sites are less relevant.
When was the last time you used a browser that had no javascript? When did you last time manually confirm a cookie?
User Experience trumps Graceful Degradation.