So many of you have noticed that we got a little surprised by WinFX Beta2. The June Customer Technical Preview (CTP) of VSTO 'v3' requires February CTP of the WinFX Runtime Components along with Beta 2 of Office 2007. Well those Windows guys went and got their Beta 2 out at the same time. So it stands to reason that you would want the Beta 2 version of WinFX instead of the old Febrary CTP.
Unfortunately, you have also noticed that the VSTO v3 CTP won't install over the Beta 2 version of WinFX. But I have good news, there is a simple workaround to enable it. The VSTO v3 CTP looks for a particular value under a particular registry key to verify that WinFX is installed. You can just add that registry key and value, and the VSTO v3 June CTP will install:
Now as you can probably guess, the problem happened because this key changed between the WinFX February CTP and Beta 2. Indigo was the code name, it is now called Windows Communication Foundation. So when Beta 2 makes its registry keys, it doesn't do an Indigo key any more, it makes a Windows Communcation Foundation key. But of course the VSTO v3 setup looks for Indigo, which isn't there .... you get the idea.
So, this should get you unblocked, as far as the install is concerned. I don't know of any problems with actually using WinFX Beta 2 instead of the February CTP version, but that doesn't mean there aren't any. With this much Beta and CTP code at the same time, there are bound to be issues. If you run into further blocking issues with this configuration, please let us know.