It’s actually very very interesting data that those links provide: they allow you to track, in Google Analytics, how much people clicked on your FeedBurner links and thus came to your site (in Google Analytics speak it’s called “campaign tracking”). I do agree that it isn’t playing nice with caching though, but there’s a better solution to this than what you’re doing now.

As Otto says, Google does use the rel=”canonical” that WordPress now offers, so it shouldn’t split PageRank anymore, BUT: it still has to crawl 2 URL’s when you get links like these.

Google Analytics allows for tracking these parameters with a hash, instead of a question mark. So, instead of:!)&

You could have:!)&

The difference is subtle, but makes all the difference for both caching and indexing. To do this, you need to slightly modify your Google Analytics tracking script though: you need to add pageTracker._setAllowAnchor(true); before the _trackPageview call. If you’ve done that, you can safely redirect the question mark version to the hash tagged version, and enjoy the benefits of both proper caching and campaign tracking.

You could use that data for all sorts of uses, I see, for instance, that you track your AdSense clicks (in a kind of roundabout way, btw), you could see whether people coming from your RSS feed actually click more or less on those ads.

Of course, if you think all of this is too much hassle, you could use my Google Analytics for WordPress plugin and check the box for “Use # instead of ? for Campaign tracking?” and for “Track AdSense”, and have all of this taken care of for you: it’ll take care of the redirects from ? to # URL’s, it’ll add the setAllowAnchor, and it’ll integrate your AdSense and Google Analytics accounts.