Second, lots of sites have made the switch from ad-less to running ads. Has there ever been a noteworthy rebellion?
For instance, you may find sponsorships, contests, and affiliate sales to be better, and better in keeping with what your audience wants from you. People actually do like advertising if it a) improves their experience, b) makes it easier to buy a good product, or c) enhances the social status of the brands they buy.
If you don't like adsense, make house ads. Even if they don't earn anything you need to see which ad products perform best.
Designers hate ads. Developers hate ads. They're ugly, they get in the way, they don't match, you need to install cumbersome systems to manage them, they create performance problems. But if they're a part of the business model then you better get used to them whether you like it or not.
And no, users really don't care as much as you think they do. They only care if you put them awkwardly in places they weren't designed to go...
I still caution anyone from overloading their new site with ads, it will definitely turn off a lot of users... especially if advertising revenue (specifically banner ads) are not a big portion of your model.
an off-the-cuff (and probably bad) metaphor: It would be insane for new restaurant to give away excellent food (a useful, ad-free site) for its first few months, and then once it had a strong clientele, start charging for a product that is not as good (same site, loaded down with ads).
Advertisements hinder user experience. Startups with the best user experience (and value) to visitors will succeed. A startup who works on implementation and user experience before monetizing the site has a better chance of success.
This is not to say you shouldn't think about how to monetize in the future.
The answer is, "it depends". I say yes, charge for your product immediately.