Strictly speaking they are minimum versions (see http://www.dotnetnuke.com/Resources/B... ), but we typically do a "soft" launch of these minimums e.g. when we did this for the move from sql 2000 to sql 2005 we went 3 or 4 releases before we used sql code that required sql 2005. This gives people an opportunity to note the new minimum specifications and move/encourage their host to move. However this is very informal, so i would not rely on it.

Note: the IIS minimum requirement is primarily because IIS6 is no longer supported by Microsoft - typically the IIS version will not effect DotNetNuke (though later releases are faster and handle more with the same hardware). Moving to IIS7 simplifies our internal testing and means we can consider items that we could not before i.e. there are a number of changes we can now make in the web.config to use IIS7 features such as filtering, compression etc. Whilst we havent any plans in the short-term for this, the changed minimum does mean we can consider these items.