Welcome to the Q&A Forum

Subdomain metrics would be the numbers tied specifically to the unique subdomain that you typed in.

Example, if you entered "www.mydomain.com", the subdomain would be "www", where if you entered "blog.mydomain.com", the subdomain would be "blog".

The metrics across all the subdomains in the domain that you are referring to would be the Root Domain Metrics.

Here's a thread from last month that should answer your question: http://www.seomoz.org/q/are-blog-comments-now-useless

Check out Pingdom, I find it useful for site speed tests, and it also lets you to run the tests out of a couple different locations.

Pingdom is showing 2.56 seconds out of Dallas Texas, and I'm seeing 2 seconds on the West Coast for your site.

Have you checked the Archived Campaigns section on the Campaigns page?