My experience with the Hudson git plugin 0.5 on Linux has been very positive. It works great.
My experience with the Hudson git plugin 0.5 on Windows has been consistently negative. I encountered Hudson bug 2762, "/ is added to path of clone destination, Windows won't clone to that destination"
When I switched to the Hudson git plugin pre-release 0.6 from stephenh (on Windows), I was able to use git on Windows with Hudson.
Stephen Haberman's improvements are mentioned at kernel trap. I confirmed that his target/git.hpi works in my Hudson version 1.290 installation. I believe it is located at http://github.com/stephenh/hudson-git2/
There is a surprising message when Hudson 1.290 starts with Stephen's plugin. Hudson reports:
Mar 10, 2009 7:57:36 AM hudson.util.RobustReflectionConverter doUnmarshal
WARNING: Cannot convert type hudson.util.DescribableList to type hudson.model.Hudson$CloudList
Mar 10, 2009 7:57:36 AM hudson.util.RobustReflectionConverter doUnmarshal
WARNING: Skipping a non-existent field repositories
com.thoughtworks.xstream.converters.reflection.NonExistentFieldException: No such field hudson.plugins.git.GitSCM.repositories
However, even with those messages, I was still able to clone my repository. I haven't done detailed testing yet, but preliminary results look promising.