More progress on my http://wiki.winehq.org/UnitTestSuites effort: Lei and I are running a buildbot that runs win32 chromium's unit tests under wine under valgrind. It just came up yesterday, and we're still working out some kinks, but you can see it at
http://build.chromium.org/buildbot/waterfall.fyi/builders/Chromium%20Linux%2...)
Running a real app's test suite under valgrind+wine can find both bugs in wine and bugs in the app; here are examples of both found today by that bot:
http://bugs.winehq.org/show_bug.cgi?id=21041 (mismatched GlobalLock/HeapFree in wine?)
http://code.google.com/p/chromium/issues/detail?id=30584 (app forgot to initialize a bitmap?)
It'll be interesting to see what else this turns up over time.