For a while I used the Item Link Clicks feature in Feedburner. For those who aren’t aware Feedburner is a service that proxies access to an RSS feed (you need to either publish the Feedburner URL as the syndication link or use a HTTP redirect to send the requests there – I use a HTTP redirect). Then when people download the feed they get it from Feedburner which is fast and reliable (unlike my blog on a bad day) and which also tracks some statistics which can be interesting.
The Item Link Clicks feature rewrites the guid URLs to point to a Feedburner URL that will redirect back to the original post (and track clicks along the way). The down-side of doing this is that some people who read blogs via Planet installations and just copy the link from the Planet page when citing a blog post instead of actually visiting the blog in question. This causes a potential problem for the person citing the post in that they won’t know whether the URL is valid unless they visit it. So when (not if) people have misconfigured blogs that are widely syndicated the people who cite them without verifying the links could end up linking to invalid URLs. The problem for the person who is cited is that such Feedburner redirects don’t seem to be counted as part of the Technorati ranking (which is a count of the number of links to a blog in the last 6 months which give some rough approximation of how important the blog is). The Technorati rating can sometimes be used in negotiations with an advertiser and is often used when boasting about how popular a blog is.
To increase my Technorati ranking I have stopped using the Feedburner URL rewriting feature. For people who view my blog directly or through a Planet installation this will not give any difference that you would notice. The problem is for people who use a service that syndicates RSS feeds and then forwards them on by email, such people received two copies of the last 10 items as the URL (GUID) change means that the posts are seen as new (Planet solves this by deleting the posts which are seen as unavailable and then creating new posts with the new URLs and no change is visible to the user).
Based on this experience I suggest not using URL rewriting services. They will hurt your technorati ranking, give little benefit (IMHO) and annoy the small number of RSS to email readers. Particularly don’t change your mind about whether to use such a feature or not. Changing the setting regularly would be really annoying. Also this means that if you use such a service you should take care not to have you Feedburner redirection ever get disabled. A minor Apache configuration error corrected a day later could end up in sending all the posts in the current feed an extra two times.