is the aspnet_compiler a pain in the A.. or is it me?

I've been trying to pre compile a asp.net webforms application to no luck. The compiler keeps coming up with errors that are not a problem if I let IIS do the compilation.

is there a different compiler that iis uses?

we have been publishing this application for years with no problem by copying over the .aspx files and the dlls in the bin folder.

The reason I'm trying to pre compile the application is so that the site doesn't slowdown to a crawl for about 30 seconds each time we publish while iis re compiles it.

any ideas? what do you do to publish .net web apps?