I can’t express how disappointed, frustrated (and more things!) I am with VS 2010 Beta 2 regarding correct behavior of commandbars for add-ins. It seems that once a bug is fixed in a VS 2010 build and an add-in can pass that point, new bugs surface that prevent its correct loading (and I have tested several builds since Beta 1).
Suffice to make you aware of these bugs:
VS 2010 Beta 2 Bug: CommandBarButton of add-in duplicated in new commandbar when already created in another commandbar
(For my MZ-Tools add-in with tons of buttons, menus and popups, only that bug of VS 2010 Beta 2 has completely ruined it, not to mention the time it took me to isolate it until I realized what was happening because initially the add-in seemed to hang, due to the number of duplications that were occurring at the glacial speed of VS 2010 debugging an add-in on another VS 2010 instance on a virtual machine)
VS 2010 Beta 2 Bug: CommandBarButton.Style not honored, always Icon + Caption
VS 2010 Beta 2 Bug: System.AccessViolationException attempting to create a temporary popup commandbar
VS 2010 Beta2: InvalidCastException casting
DirectCast(CommandBarControl, CommandBarPopup).CommandBar.Parent back to CommandBarControl
I realize that changing the COM-based commandbars of VS 2008 by new WPF-based commandbars in VS 2010 is a daunting and difficult task, but if the next milestone after Beta 2 is Release Candidate (where only critical bugs are fixed) then Beta 2 should be already free of such nasty bugs. Or there should be a known roadmap of betas / CTPs until RTM so that developers of add-ins can know how many builds they will have to test and rest assured that they will have enough weeks/months to test their add-ins (considering that in Beta 2 they can’t get them even loaded in Visual Studio).
I think that since Microsoft builds and extends Visual Studio with packages (SDK) and not add-ins, commandbars/commands/buttons of packages get better behavior earlier in the development cycle of Visual Studio. But for add-ins (automation) every time that commandbars are changed in some VS release, you have to wait until the RTM to check is some bug that could ruin your add-in is fixed. I experienced the same with VS 2005, which introduced 24-bit bitmaps (rather than the 16-color bitmaps of VS.NET 2003) and a different assembly for Microsoft.VisualStudio.Commandbars.