Okay,
URL Routing is great. Extensionless URLS, SEO friendly etc. However, it seems that IIS 6 doesn't perform compression on sites that use Extensionless URLs.
WildCard Mapping is on so Asp.Net can process the extensionless files, but is there any way to set these resources to be gzipped?
Perhaps the following product may be useful: Port80's httpZip
Disclaimer: I haven't tried the product, and don't have any affiliation with the company. I've simply been keeping it on my radar in case bandwidth costs ever went through the roof, after I learned IIS6 built in compression wasn't the bees knees.
One of the httpZip FAQ pages states: "Controlling compression by MIME type: IIS 6.0 built-in compression uses the file extension and/or location to determine whether a file should be compressed or not. If you need to control HTTP compression by MIME (for example, if you have an application file like ASP or an ISAPI filter that is outputting content with different MIMEs), httpZip's granular controls for compression by MIME type are the only way to accomplish this on IIS 6.0."
To address the point raised in JackM's comment, one of the product's claims (at the first link above) is "Flawless decompression ensured by real-time browser compatibility checking. [... then later ...] IIS 6.0 on Windows Server 2003: A robust compression engine is built into the Web server, but suffers from a fatal flaw – it lacks browser compatibility checking."