Here I am plugging an other thread at SearchEngineWatch Forums, I am sorry, but the quality of threads over here are simply outstanding. A thread started by the famous Search Engine Strategies speaker and SEM expert from Denmark, Mikkel deMib Svendsen, discussed the benefits of using mod_rewrite to make a dynamic site search engine friendly. Post # 5 at this thread is where this discussion begins.
Mikkel is a huge fan of the mod_rewrite and so am I. As we discussed, its an easy way to convert dynamic looking URLs into search engine friendly URLs. This instantaneously makes more of the "hidden Web" visible to the search engines and searchers. Besides for the SEO benefits of mod_rewrite, you can use it for a dozen reasons. On some of my sites, we use it for authenticating traffic and access to files, so if someone tries to rip off stock photos from a client's site - it will mask the photo as stolen and strike it out. That is just one example of other uses for mod_rewrite, you can come up with really smart uses, depending on the time and ideas you have.
Ron Carnell tends to argue with this practice of using mod_rewrite or the other URL rewriting techniques on sites. In fact, he says that its a last resort action and should be considered a band aid like approach as opposed to a perfect solution.
If your CMS isn't SE-friendly, that's a problem with the CMS, not with the web server, and the best solution will be implemented at the correct level. Realistically, I know it's not always possible to solve the problem at the source, but I think that should always be the goal. At the end of the day, mod_rewrite is typically a Band-Aid used to cover up sloppy programming. Heal the wound, and the Band-Aid can be removed.
This makes for an interesting thread, feel free to join in.