Whether it's responsive design or a mobile site, it does require really thinking about user intent (which more people should do anyway but I digress)
My mobile users mostly come to the site to look up the date, time and/or location of an event, they have no need for (and traditionally don't visit) the rest of the site. They get a shortened menu and a more mobile-friendly layout, with the option to go full site if they want.
That plus the ad situation made me go mobile plugin for them.
On my own personal site, where there's no ads, I love the responsive design - the sidebar content is nicely tucked underneath the 'meat' and it seems to work well in everything. I assume anyone coming there is coming to read, because there's no other reason to be there, regardless of device. So they get everything.
There really isn't a one size fits all solution yet - but we're a lot closer than we used to be.