1st. bug: I haven't noticed it yet. But I haven't used the new Qt5/QtCreator2.6.1 for very long.

2nd. bug: Confirmed. Seems there's still a naming mixup between quick1 and declarative here and there. The docs claim that .pro files should have QT += quick1 to use the old Quick1 module (which is what we are using when adding a QDeclarativeView). But it seem to only accept QT+=declarative.
It is odd about the wrong include file: I have recompiled the QtDesigner plugin and checked that Src/qtquick1/tools/designer/src/plugins/qdeclarativeview/qdeclarativeview_plugin.cpp and Src/plugins/qdeclarativeview/qdeclarativeview_plugin.cpp both have the correct line:
Qt Code: 
  1. QString QDeclarativeViewPlugin::includeFile() const
  2. {
  3.     return QStringLiteral("QtDeclarative/QDeclarativeView");
  4. }
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I've recompiled the plugin and put the DLL in Tools\QtCreator\bin\designer and 5.0.0\msvc2010\plugins\designer but I still see the wrong include (QtQuick1/QDeclarativeView)