It is a great way to block ads within Opera. I have used this for several years and have not seen ads for some time. Some sites still have them. but all you have to do is view the code of the page, find where the ad is and add it to the filter using notepad. Ad gone.
For IE i have tried IE7Pro with Ie8 and it is a no go. But there is a InPrivate Filter that you can use with IE8 by default to block most ads. It is crossed over from the Ad Block of Firefox to a rule.xml file that IE can read.
Here is a older list. I know some sites have more up to date lists that block more ads. There is one that also has a Registry File that you can have IE8 load up using InPrivate Filter mode at all times instead of having to load it up each time you load IE8.