Not surprising...
"However, Microsoft also warned that the beta breaks the Visual Studio Async CTP tool and it also plays havoc with Razor IntelliSense for those punters who have the ASP.NET MVC 3 RC installed."
So, a beta SP1 for VS2010 may break the 'betas' (okay Community Technology Preview, and Release Candidates) of other unfinished add-ons. Hardly surprising (or fair to criticise) - although worth warning people to wait a bit before installing if they use any of those add-ons.
What will happen is that the teams who did the other add-ons will update theirs to work with the new beta. I believe the MVC3 team have said they'll have theirs available on Friday.