Folks that are on early betas of products (especially private betas) are not surprised when projects are not updatable between beta versions. These limits are usually listed in the release notes, sometimes you'll just stumble across them.
I'm getting back into SQL Server 2008 R2 and related features in earnest (since my presentation in Portland in September) after a busy November and December and noticed early on that PowerPivot workbooks weren't updateable between CTP2 and CTP3.
Lately I found that maps from BI Dev Studio Report Projects from the August CTP don't upgrade to the November CTP. Although it says the project upgrades, the maps are unusable. However, there is a workaround (I bet you wondered when I'd start including useful information in this post . Just create a new report project in BI Dev Studio November CTP. Then, move the .rdl, .rdl.data, and .mds files from the old to new project. Voila! Maps!