Trawling through Microsoft.TeamFoundation.Build I found the flag for IncrementalGet. Not getting full sources every time has cut 40 seconds out of every build. This is particularly useful when debugging a build script.

Buck Hodges discusses IncrementalGet and IncrementalBuild and links to Martin Woodward's 30 Useful Team Build Properties. Not sure I'm ready for IncrementalBuild yet, I like having shiny new dll's.

This is what I added to my root level PropertyGroup just before DropLocation:

    <!-- INCREMENTAL GET

      Setting this flag will set:

      CleanCompilationOutputOnly: true

      SkipInitializeWorkspace: true

      ForceGet: false

      (Microsoft.TeamFoundation.Build Line:379)

    -->

    <IncrementalGet>true</IncrementalGet>