Dave McKinstry has written a couple of posts on his experiences with Team Build in TFS 2008.  In Introduction to Team Build 2008 for Team Build 2005 Users, he goes over the major new features and how certain things like handling workspace mappings are improved over TFS 2005.  His post includes screenshots and more.  It's a great companion to the basic guide post.  I can't help but quote a couple parts that I enjoyed the most.

If you haven't already gotten a chance to play with TFS 2008 (Beta 2), I recommend it.  My experience is that it is solid and seems to work better than the RCs worked for the 2005 release.  My primary interest is in the Team Build enhancements, although there are a few other interesting TFS 2008 features such as Destroy and the integration of key TFS Power Tool elements.

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There are certainly other changes in Team Build 2008, but this should summarize all of the significant change.  I rarely recommend prerelease software for any of my clients.  However due to the vast enhancements in Continuous Integration support (i.e., triggers, queuing and retention policies), both my company and one of my customers are using TFS 2008 Beta 2 and it's go-live license.  Note that for my client, the users are still using Visual Studio 2005 and Team Explorer 2005...  but the Team System back end is all 2008!

He also writes about considerations in using TFS 2008 with VS 2005 clients.  The post points out how it is important to have at least someone on the team who also has VS 2008 installed (or at least Team Explorer 2008) to be able to access and configure the new features available on TFS 2008.  Once someone has configured build definitions for CI, for example, folks using VS 2005 automatically get the benefit of CI (even though they can't see the build queue, for example).