I have two 2560x1440 monitors running off an ATI Radeon 6970 on Windows 7.
Before reformatting, I had adjusted the DPI to 120 via Control Panel > Appearance and Personalization > Display > "Medium - 125%". I am not entirely sure, but I think I had checked "Use Windows XP style DPI scaling" (which is the default for DPI less than 144 I believe). My apps looked fine; the text size was larger, but it never really caused any problems.
However, upon reformatting, I tried to do the same thing and have ended up with messed up text and icons in my apps. Examples:
In Outlook, the icons are resized in crazy ways and look much worse, and the text---except for the actual message list---is oversized.
In muTorrent, the text is too large to fit in its bounding boxes, and gets clipped.
I have tried right-clicking on the program and choosing Properties > Compatibility > Disable display scaling on high DPI settings; this does nothing.
Also of note: in Windows Explorer, things look fine; the text is not comically oversized and the icons are not scaled up.