FYI, you can run this through the Visual Studio command prompt or just directly call it. This file is located "C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_compiler.exe".
However, if you're still getting very poor responsiveness for the first page request, you can try some other things:
1) Put the website in it's own application pool2) Place a standard .html file in the site and see if it takes as long as the .aspx pages do