In our company we are currently working with VS2008 and office 2003.  Everything will be upgrade to VS2010 and Office 2010 the comming months.
But some developers already have VS2010.

Since the moment that they have it installed they had problems with VS2008 connecting to excel.
They always got the error "TF86001: Team Foundation was unable to load the office addin" and "TF80042: The document cannot be opened because you don't have Microsoft Excel 2003 or later, or one of its components installed".

The problem is caused bacause of the installation of VS2010.  Here you need at least office 2007 or higher.

The solution for this is easy.  Just follow the next steps:

1) Open a command prompt in admin mode
2) Change the directory to "Program Files\Microsoft Visual Studio 10.0\Common7\IDE\PrivateAssemblies"
3) Unregister the 2010 add-in version: "regsvr32 /u TFSOfficeAdd-in.dll"
4) Chnage the directory to "Program Files\Microsoft Visual Studio 9\Common7\IDE\PrivateAssemblies" (could also 9.0 instead of 9)
4) Register the 2008 add-in version: "regsvr32 TFSOfficeAdd-in.dll"

This will  disable the office integration in VS2010 and enable it again in VS2008.  You cannot use the tree queries, it has only the ability for flat queries.
Also you can only use VS2008 and not VS2010 for the export to excel.

If you repair your Team Explorer,there is a big change you have to do these steps again.

What if we upgrade to Office 2007 or higher after this change?  Easy just the the opposite.  Unregister the VS2008 add-in and register the VS2010 add-in.

Yep, finally it's there.  The new VS2010 and .Net 4.0.  Yesterday was the lauch event of it.  And if you're a MS subscriber, then you can download it now from your subscribtion.  So go there, login, download and install it and enjoy this great new release.

You can still see the launch event if you have missed it, just go here: http://www.microsoft.com/visualstudio/en-us/watch-it-live.

For more info go to Scott Guthrie's blog and read this article: http://weblogs.asp.net/scottgu/archive/2010/04/12/visual-studio-2010-and-net-4-released.aspx.

Also, txs to my friend Kris van der Mast, here's a link for e free eBook about VS2010: http://blog.krisvandermast.com/ct.ashx?id=9e36e215-e443-442d-8427-6140ba274408&url=http%3a%2f%2fwww.microsoft.com%2fdownloads%2fdetails.aspx%3fdisplaylang%3den%26FamilyID%3d12a6de81-c633-4f2c-a35f-cea6fe772712. 

The book is not a language primer, a language reference, or a single technology book. It's a book that will help professional developers move from previous versions of Visual Studio (starting with 2003 and on up). It will cover the features of Visual Studio 2010 through an application. It will go through a lot of the exciting new language features and new versions of the most popular technologies without putting the emphasis on the technologies themselves. It will instead put the emphasis on how you would get to those new tools and features from Visual Studio 2010.

MVP, Jeff Levinson, has created a nice Work item visualization tool (first version).  This tool turns work item relationschip information into some nice DGML graphs.  These graphs can be viewed  in the new architecture visualization tools.

You can find this great tool at codeplex: http://visualization.codeplex.com/. So go there, download it, use it, etst it and give feedback to improve the tool.

Some announcements about VS2010:

1. MS Visual Studio Test Elements 2010 will be renamed to MS Visual Studio Test Professional 2010
2. MS Test and Lab Manager will be renamed to MS Test Manager 2010
3. MS Visual Studio Team Lab  Management 2010 will be renamed to MS Visual Studio Lab Management 2010
4. Pricing details for VS2010 are release

All this info and a bit more background info can be found here http://blogs.msdn.com/slange/archive/2010/01/26/it-s-official-vs-2010-branding-pricing.aspx.