With my most recent piece, I've been hearing that much of what is holding people back from using IE8 is the lack of an Ad blocking feature.
Perhaps not widely known, but IE8 actually contains a great Ad blocking feature built-in, it's called "InPrivate Filtering". The InPrivate Filter (enabled by pressing CTRL+SHIFT+F) is intended to block content that may potentially share your information; thankfully advertisements are one such example of said content.
It should be noted that the InPrivate Filter is 'smart' in the sense that it can and will (if enabled) automatically detect content which appears with a high frequency on websites that you visit. In this regard, the Filter learns as you use the web and can detect what is an advertisement or of similar content, and take action accordingly. By entering the 'Manage Addons' window, you can select how many websites a piece of content must show up on before it is flagged, at which point you can then determine whether you want to block or allow such content.
For example, if out of 10 website you visit, IE8 sees that a URL is repeated (i.e. blahblah.advertisingsite.net), on 3 different websites (you can change this value) it will show up in your list, at which point you can choose to block it. You may also just tell IE to automatically block such content.
Given the functionality of the InPrivate Filter, it seems that all that is required is a "Subscription List" containing the locations of advertisements for the filter to function as other Adblock applications. This is similar to a "Block List" in Adblock Pro and equivalent software. With such a list, it should be possible to simply block certain locations outright without relying on IE to learn from your browsing habits.
To Enable InPrivate Filtering
In IE8, under the "Safety" button ensure that "InPrivate Filtering" is enabled. You can tell it is enabled by the checkmark that will appear next to the text.
Directly under that button you will see "InPrivate Filtering settings". You now have a list of content that has been flagged by IE8 based on the frequency it has shown up. The default frequency is "10", meaning that in order for a piece of content to be flagged it must appear across 10 websites. You may change this frequency in the appropriate box to a minimum of 3 or a maximum of 30.
On top of the box which lists said content, you have a couple of radio buttons. The first, "Automatically block" will simply block outright any content which matches the criteria of appearance on 3 (for example) or more websites.
With regards to a subscription list that will block advertisements outright without having to 'learn' your browsing habits, I am in the process of searching for such. I have stumbled across this link where someone has compiled an XML file of the blocked URL's from Adblock Plus.
In order to Import these URL's into the InPrivate Filter, you must enter your "Manage Addons" window, accessible via Tools > Manage Addons. Click the InPrivate Filtering button, followed by Import and then locate the XML file. The result should be IE8 blocking content from said providers outright, without the need to learn via your browsing habits. Doing so has blocked about 99% of the advertisements I see while browsing with IE8.