StandardZilla has a great blog entry about "How to Evaluate Your Website in 30 Seconds."  There some easy to use techniques that will give you a quick feel for how the web site will perform for many different users.  Additionally, there is another entry on "Case Studies - Evaluate Your Website in 30 Seconds."  Below is an excerpt:

 "What this test will tell you in under 30 seconds:

Does the website work with CSS off?

Does the website work with Javascript disabled?

is the website using tables for layout, instead of CSS?

is all essential information in the HTML?

is there extra code, non-essential information in the HTML?

is the site all Flash?

is there hidden content?

is image replacement being used?"