Err ... even Microsoft marketing stuff (dead link) is messy! (says both IIS 7.0 and 7.5). However, I believe that Windows Server 2008 Web comes with IIS 7.0 and Windows Server 2008 R2 Web comes with IIS 7.5 FYI.
And yes, if you have an application working on IIS 7, it works fine on IIS 7.5.
Edit: appears Microsoft updates its site from the moment of its publication, leaving a link for everyone who is looking for information on the server and R2 server.
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