Here are some quick first impressions.

• In the code editor, you can now use the ctrl + mouse wheel to zoom in and out of code. It sounds kind of underwhelming, but in practice this feature i
• When debugging you can "pin" data tool-tips (called data-tips) to quickly keep track of variable values. It's quick, easy, and very convenient. Here is a more detailed description with pictures.
• The user interface has been overhauled (using WPF I believe). It feels a bit "heavier" due to the use of darker colors, and will take some time to get used to.
• The improved multi-monitor support is great and will definitely improve my productivity..
• I miss the old Visual Studio logo. OK, that's not a feature, but I really don't like the new one :-)
• The naming of the new versions are possibly more difficult to understand because of more generic names, but I am happy to see them consolidating functionality, and offering fewer versions to choose from. Ultimately, I wished they offered a single version, or maybe at most a "standard" version, and then a "test" version with just the testing tools, as that would be useful to deploy to test workstations.
  
  • Previously Visual Studio consisted of the following:
    
    • Express
    • Standard
    • Professional
    • Team Foundation Test
    • Team Foundation Developer
    • Team Foundation Database
    • Team Foundation Architect
  • Visual Studio 2010 consists of:
    
    • Express: Free version with reduced functionality.
    • Professional: For developers.
    • Premium: For developers, testers, and DBAs with some of the design and modeling tools.
    • Ultimate: Contains all VS features and functionality, with additional ALM functionality as well as full design and modeling tools.
    • Test: Contains only the testing tools.

Overall my impressions are positive. I'm working on migrating one of my projects over to VS2010 (but not .NET 4.0 yet) tonight and so far it's been easy. I can already see some productivity gains in VS2010.