Precompilation will help you tremendously with the initial response time. First-load times of pages on a precompiled site may be even 10x faster. Of course, it depends on the number of controls and virtual objects used on the pages. However, after a page is loaded, the controls, web parts, pages and virtual objects are compiled and moved to the "Temporary ASP.NET files". So the performance of non-precompiled projects is as good as precompiled projects on subsequent requests.
Does it seem worth it? Have you considered Application Initialization in IIS
FYI: We compared both types of projects (web site, web application and precompiled web site) and our tests have shown that the most expensive part of compilation is the markup of controls and virtual objects. There wasn't a big difference between web site and web application projects. When Temporary ASP.NET files contain compiled controls and virtual objects, the performance of both types of projects is basically the same even after an IIS or application restart.
More info about precompilation: http://msdn.microsoft.com/en-us/library/bb398860(v=vs.110).aspx