Performance of content aggregation queries on multiple lists

Recently I got the task of creating a custom content aggregation Web Part which would roll up content from two lists. As this can be done in many different ways, I've decided to do a little research on which of these methods would perform the best.

Accessible 404 (PageNotFound) in Microsoft Office SharePoint Server 2007

Every time you request a web page that doesn't exist, the web server provides you with a 404 (the web server response code for an non existing URL) page - an information page telling you that you've got it wrong. While some of your visitors, might be able to get to the information they are looking for either by correcting the URL or finding an alternative way to access the resource, it is a good practice to provide an information page which will help the average visitors to continue the navigation like nothing really happened.

Semantic URL's in MOSS 2007 (Imtech SharePoint Semantic URL's free Feature)

Semantic URL's are one of the things I always wanted to have in Microsoft Office SharePoint Server 2007. Since the first time I have opened an Internet facing site made in SharePoint 2007 I knew it would be great if the Pages part of the URL could be removed as well as the .aspx extension.