What’s the downside to using your own domain and WordPress’ domain mapping service?

A website that is slower than 100% of all other websites.

From Google’s new Webmaster Tools Site Performance tool:

On average, pages in your site take 38.3 seconds to load (updated on Dec 3, 2009). This is slower than 100% of sites. The chart below shows how your site’s average page load time has changed over the last few months. For your reference, it also shows the 20th percentile value across all sites, separating slow and fast load times.

Google Webmaster Tools Site Performance

So much for free value.

Unbelievable….