Whenever the discussion of apps with bad UI comes up, Tasker - powerful as it may be - is always one of the first to be mentioned. Because, let's face it, it's pretty hideous. In the early days of Android, this wasn't much of an issue, as there was no standard UI. Or, you know, the Android Style Guide. In the past year or so, though, Google has really been pushing a the clean look of ICS+, Holo, and a consistent experience across applications.
Google is finally showing developers what an Android app should look like. Android Design is Google's freshly launched style guide for Ice Cream Sandwich. It outlines everything developers should do to make a high quality app that "fits in" with the rest of ICS.
Most of the big stuff is covered: Icons, color swatches, grid layouts, writing style, touch feedback - it's beautiful. Apps are normally all over the place, it will be really nice to see some consistency.