First of all no matter how much it seems like "everyone's using AdBlock" the only people who are using it, is "us." And who are we? The tech-savvy, the people who use the internet all the time, the nerds if you wish to call us. There are only 8 million people that use AdBlock daily compared to the one billion and five hundred million internet users means that the percentage of people who use AdBlock is 0.053% of the internet users. And the people who use AdBlock are the people who hate advertising and would not click on ad without it. For the people who are complaining about their Adsense revenues going down, it's not because AdBlock. Who agrees? I find AdBlock a good program if you would never click on an ad anyway. I am only against the computers being preloaded with adblock, and that is not happening.
It really depends on your niche. If you have a blog or web site targeted toward the tech-savvy or internet marketers you are likely to be affected, both by adblock and "ad blindness". On the other hand, if most of the visitors to your site aren't hard-core internet users, then it might not affect you at all. So who knows? I'm pretty sure that Adblock/Adblock Plus only works with Firefox, so if the majority of your visitors are using IE, you probably don't need to worry about that so much.