The size of the application definately plays a big role in deciding whether or not to pre-compile. Applications the size of DNN will benefit from it greatly, although applications of that size are fairly rare.

I love the fact that I can now use code-behind in my open source applications without the need to pre-compile. Previously, users who didn't have VS or couldn't figure out how to use the command line compiler had a lot of difficulty making changes to the source code - and the process was very cumbersome. I resorted to using single file .aspx pages to make things easier for them. Now however, I can make use of code-behind and my users don't have to worry about compiling the code. Since my open source application compiles almost instantly, the performance benefit is almost nil.

Thanks! Ironically, this skin is the simplest one I have done so far, but it's also my favourite :)

That folder is for the default SQL Express MDF.  If you're using SQL Server 2000/2005 I would think you could delete it, but once this file is in place, it will never be touched.  I don't get the point about 1.2MB on transfers, unless you are severely restricted and don't want to move it at all.  If you've never used it, I wouldn't think it matters.  Maybe someone who has deleted it could chime in.