First, I want to welcome Shane Bishop the newest Foo Theory blogger! Shane is one of those band members that worked at ********* with us back in the day but I didn't actually meet him until he came on at Statera: you know - different clients - we get busy... He's a good guy, he knows his stuff and we look forward to his involvement. Take a look at his Foo Theory blog here.
So most of the people reading this blog are likely to have come across issues with prior Beta product upgrades. In particular, when upgrading previous Visual Studio betas you would seriously consider re-imaging your machine. In this post I'll share my experience of upgrading my Vista laptop which side-by-sides VS 2005 and Visual Studio Orcas Beta 1 to VS 2005 and VS Orcas (2008) Beta 2. I'll point out that I, like many other, have a considerable amount of VS 2K5 extensions installed that I still rely on. The Beta 1 readme indicated that you should be able to install later Beta versions but will require a repair to VS 2K5 after uninstalling Beta 1. This indicated to me that the DivDev folks expected for the upgrade to be a reasonable undertaking and that they had some confidence that it would work.
In general I'm less exposed than some as I didn't install a whole lot of add-ins like Orcas Silverlight tools and Orcas ASP.NET Futures. I'd think this pretty typical, though, as there's a lot to digest in the Orcas line-up already. I did, however, install (or configure) ReSharper (R#) for Orcas but I was familiar with the needs here as the JetBrains folks have been pretty helpful.
In this post I'll track my upgrade experience start to finish: good, bad and ugly. So let's get started:
An initial lay-of-the-land looks something like the following (Programs and Features sorted by date). Hmm - don't remember installing all that!
Ok, Ok - yes, it took me a week and a half to pull down and install it. Cut me some slack: I have a life too! 
.. So ..
1) Uninstall MSDN Library for Visual Studio Codename Orcas
2) Uninstall Microsoft Visual Studio Codename Orcas Team Suite - ENU
Take a look at the installation/Uninstall components below. Hey those look familiar.
Below are the result of step 2, again, showing Programs and Features.
Hold on: one thing stands out and it was installed on 5/12 the day I installed Orcas Beta 1 - Microsoft Visual Studio Web Authoring Component. As I don't remember installing any VS 2005 or Orcas components that day (a few months ago) I did a Google search. I found a post by Rick Strahl pointing out that he'd had a problem with the installation of Beta 2 as a result, ultimately, of not uninstalling this component. Thanks Rick for providing a heads-up on this...
3) Uninstall Microsoft Visual Studio Web Authoring Component
As a note: Scott Guthrie's (ScottGu) blog confirms the Orcas Beta 1 release notes: you should run a repair on VS 2005 after uninstalling Beta 1.
4) Repair the VS 2005 installation
The VS 2K5 repair ran without incident though it did take quite a long while to complete. Make sure you don't need your machine for a while when you kick it off. I'm one of those anal types that don't like to have a bunch of stuff running during critical installations. Admittedly, though, I had Outlook up at times.
Testing after the repair revealed that all of the VS 2005 extensions installed previously were working as expected including ASP.NET AJAX, Guidance Automation Extensions/Guidance Automation Toolkit, Enterprise Library and Service Factory. There were two exceptions but not a big deal as I can re-install them later: ReSharper (as mentioned above) and Regionerate. I'll provide an update if I find other issues after I publish this post.
5) Install Visual Studio Orcas Beta 2 (or 2008 Beta 2) - I chose to do a Full Install
During the installation Microsoft .NET Framework v3.5 required a restart of the machine. In addition, the following warning was generated.
After researching the above warning the only relevant information I could find was in the Orcas Beta 1 Readme where it mentions the following (at section 1.1.15): "Installing Orcas on Vista may prompt to close running applications such as Machine Debug Manager." The resolution in the readme is to select Ignore and continue with the installation. BTW: the Visual Studio 2008 Beta 2 readme does not mention this explicitly but does suggest killing all applications in the warning list. My suggestion: review them both and "choose wisely". So after killing 1088 and Ignoring MDM - I march on.
In the end the install was a long one but seemed shorter than the VS 2K5 repair: actually fell asleep during the repair last night. So the installation went as expected from here and resulted in a successful install. Almost there. Almost there. Stay on target ...
Oh @$%! - did I just nerd out in public? Pull it together - Matt. ... So ...
You'd be crazy to not install integrated MSDN documentation IMO. As there's a lot to uptake with Orcas, .NET 3.0 and 3.5 new designers, ya-da-ya-da: MSDN documentation will be a launching point.
6) Install Product Documentation - optional (MSDN)
Finally, there are some follow-up tasks. Scott Guthrie provides additional context on these steps in his VS 2008 Beta 2 post (in the section "Important Installation Notes - PLEASE READ!"):
7) If you have existing projects using ASP.NET AJAX 1.0 and built using VS 2K5 extract and install the script described in step 3 of the Beta 2 installation instructions. More information on the script can be found here. Note: the script must be run as administrator.
8) If you've installed previous version of VS Orcas/2008 (CTP/Beta 1) reset VS settings by executing "devenv /resetsettings" from the VS 2008 command prompt.
That's it: you're ready to roll!
So I've been using Orcas now for a few months almost exclusively for EDD and POC development. I'll be posting over the next bit on my experiences - good and bad. Heck - good and wish list. All-in-all it was a smooth beta upgrade that most should be able to live with: thanks VS team (DevDiv) for taking the time.
Have fun! And hope this helps...