Is there any setting in IIS 7.5 to prevent it from recycling the app pool when a default document is changed?
IIRC this didn't happen in IIS 6 and I want that behavior back.
This is caused by delegated configuration. In IIS7+, the settings can be written to web.config (and they do by default). Touching web.config causes an appdomain recycle.
You have a couple solutions. One is to turn of delegated configuration, but that comes with considerations, like ensuring that you don't already have settings in your web.config files, which will cause the sites to break.
Another option is to use Configuration Editor or a text editor to apply your settings to applicationHost.config instead of web.config.
To see further information you can watch week 17 of my video series on IIS.