Over on the "ACE Team" blog there's a useful blog post with some performance tips for ASP.NET sites. The point about batch compilation and Debug="true" was certainly correct for version 1.1 but I think in ASP.NET 2.0 they are decoupled - so by default batch compilation remains on when debug="true". That was my own experience anyway.
It also links over to another very useful post which fulfils something a customer was asking me about just recently - how to "warm up" an ASP.NET site to ensure all pages are compiled (assuming you are not using the pre-compiled model).
And I cam across those two links by chance when I was reading this interesting post about correctly simulating browser caching when performing load tests with VSTS 2008.