If you're wondering whether it's worth fixing Valgrind warnings (after all, they are just warnings, right?):
First, some of the valgrind errors that show up when running the test suite might be real bugs. That might be enough reason right there.
Second, clearing out the valgrind errors that show up in the test suite make it a lot easier to find Wine bugs when running real apps on wine on valgrind. (The lower the background noise level, the easier it is to see the real problem.)
Third, if valgrind works well on wine, windows developers might start coming to Wine just to run Valgrind on their apps to find app bugs. (Don't laugh! It could happen!)
This is why I hired John Reiser to improve Valgrind/Wine support, why I've been fixing a few valgrind warnings lately, and why I think it's important for other people to start doing it, too.
That said, it's important when fixing Valgrind errors to really understand the code you're changing, lest you paper over a bug with another bug, or make things worse. (Here would be a good place for me to thank James for his code reviews :-) - Dan