Hi Fernando;
Dale is correct ... EAS is basically at its EOL. IIs is not a real application server .. its a Web server thinks is an application server ("wannabe") and can not compete with the likes of the mature J2EE application servers in either performance or feature set.
The only exception to IIS's application server handicaps is when you add something like the Appeon Server into the mix that is really an IIs "Helper" to significantly boost IIS's lack of full application server features.
MS is of course counting on the fact that you will use IIs and once hooked - will want to seel you on a "farm" of servers, OS licenses, etc to compensate for IIS's les than stellar single machine performance.
IMHO ... SAP should bring back DPB to replace EAServer and kick some Application Server "***" - both in the performance and price areas!
Regards ... Chris