Internet Explorer 8 removed support for one of my favorite browser features: Inline AutoComplete (IAC) for the address bar. This feature was off-by-default, but for almost a decade the first thing I did when setting up a new computer was enable IAC using the checkbox Tools > Internet Options > Advanced > Use inline AutoComplete.
For IE8, we introduced a new Smart Address Bar which offers a bunch of improvements including better and more relevant suggestions in the new flyout window. The feature also includes keyboard tips, which show how to take advantage of keyboard combos to open pages in new tabs, background tabs, etc. Unfortunately, as a consequence of the rewrite, we lost the legacy AutoComplete behavior provided by the Shell. The consensus was that, while IAC had some vocal proponents (myself especially), the fact that it was off-by-default and most users didn't have it enabled meant that it was a reasonable sacrifice when compared to the benefits brought by the new address bar. The most important improvement for keyboard lovers was the SHIFT+Enter hotkey, which navigates to the "best match" in the results list; there have long been complaints and debates about whether the default behavior of IAC was suboptimal. With the relevance engine added to IE8, we have good reason to believe that SHIFT+Enter is a great feature for most folks to more quickly get to the best result.
Nevertheless, I expected that we'd hear from vocal proponents of IAC during the IE8 beta cycles. The initial blog post announcing the change had a few heated comments, and one bug with a meager 16 votes was filed on Connect, but we didn't receive nearly the level of feedback I was expecting. After two betas and one release-candidate which were used by many millions of users, I could only count a handful of supporters for IAC. Since we shipped the final version of IE8, I've received more mail asking why IAC was removed. The gist of much of the feedback was "You already had the feature, it wouldn't have cost you anything to keep it." Unfortunately, that's simply not true-- IE8 is no longer using the standard controls that support AutoComplete, and even if was, the "free" AutoComplete behavior wouldn't work as expected with the matches in the Smart Address Bar's dropdown.
IE8 has been my default browser for quite a while now, and I've largely adjusted to the change. Beyond getting used to the SHIFT+Enter shortcut, I also heavily use SlickRun, a keyboard-lovers' utility I wrote a long time ago which makes heavy use of command aliasing and offers Inline AutoComplete.
As we build future versions of IE, I encourage you to provide feedback early and often. We've already received some great suggestions from the web developers out there, but we're very interested in UI suggestions as well!