Ask HN: What's your take on using ads for non-paying users?

I'm working with a startup on rolling out a sweet product. In our last meeting we spoke about differentiators for premium accounts and what we could offer to make it worth the money. Obviously, the notion of ads came up for free accounts (which would be disabled if you had a paid account).

I'm not a fan or flashy ads or crap like that. I feel it breaks the "feel" of the simple and clean website we have. I was thinking about using a service which allowed me to use text-only ads and style them in such a way that they fit into the website a lot more. Then I realized I've never seen a startup website that had ads at all.

Is this a good idea? The ads aren't meant to be a major revenue stream, they would pretty much only be introduced to "sweeten" the paid plan.