Its nice to have the following features in the next release of ARR/URL rewrite
1) Ability to include complete list of IIS Server Variables.
2) Ability to define a rule to or not to rewrite request headers based on a condition (either POST value or request header value)
What I noticed is ARR rewrites request headers but with rules we cannot modify certain request headers like HTTP_REFERER etc.
3) Ability to inject C# code for pre and post request, response. The only way possible to do this is to define a HTTP module(only response stream can be modified not request).
4) Ability to define a rule that rewrites request header based on response stream matched value (with regex). Its not possible to modify response header by searching a response stream value.