Sometimes query strings can differ for a reason un related to performance and you want to have them ignored as all pages that are identical before the ? mark have the same characteristics.
Thanks to rachenj who submitted the bug to Show Slow bug tracker, now we have this feature.
Configuring query string pruning is easy, just set $dropQueryStrings = true if you want to drop all query strings or set it to an array of URL prefixes to match.
You can find full documentation on the wiki:
http://www.showslow.org/Installation#Drop_query_strings_from_URLs
Go ahead and download latest code from trunk:
http://code.google.com/p/showslow/source/checkout
Have fun and post your suggestions to the mailing list and bug reports to the issue tracker.