No, you should not use %logonserver% either.
Since sysvol is replicated to all DCs you can specify \\domain.tld instead. In fact, I find XP boxes to be much faster using \\domain.tld instead of %logonserver%.
If you put all the files in the funky GUID folder, you should be able to get by with relative paths but I prefer to use a BATch file instead.
If you have multiple GPOs would you have multiple copies of KiX salted around? Who wants to open GPMC every time you want to edit the script? Worse yet, who wants to drill down that horrible path to get to the scripts folder? Create a folder structure that matches your OU tree and put your scripts there. All you need in the funky GUID path is the BATch that calls KiX and the script.
There is a FAQ on this subject.
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Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.
