A user sent me this blurb out of Wrox's ASP 3.0 Programmer's Reference regarding the differences between Server.Transfer and Response.Redirect:
The current page's context is also passed to the target page or resource. This includes the values of all the variables in all the intrinsic ASP objects, such as the collections of the Request, Response, and Session objects, and all their properties. The Application object context is also transferred, even if the page is within a different virtual application. The current transaction context is also passed to the new page, allowing it to take part seamlessly in any current transaction.
Meanwhile, the browser's address bar still shows the original URL, and the Back, Forward, and Refresh buttons work normally. When we use client-side redirection, especially with an HTML meta tag, this usually isn't the case.
However, the values of any script variables or object references that were created or set within the first page are not available within the new page.
One other major difference is that because Server.Transfer doesn't require the client to request another page, it can be faster in some cases, depending on what you're doing.