I have Sharepoint 2007, and I am going to buy Visual Studio for the first time. Does Visual Studio 2010 work with Sharepoint 2007?
Yes of course it does. But be aware of the different versions of Visual Studio.
VS 2010 you can build workflows, list definitions, site definitions, web parts, etc. etc.
You can't buy Visual Studio 2010 yet. It's not due to be released until this spring.
Unfortunately no. Visual studio 2010 has integrated lots of features which can be integrated and deployed to SharePoint 2010 only. Because of lot of variations like system versions [32/64 bit and architecture] it won't support 2007 system.
But, you can open your custom projects or solutions in Visual Studio 2010 and manually deploy them to SharePoint 2007 as you are doing using Visual studio 2005 or 2008.
You can't automatic configure or deploy to Sharepoint 2007 using VS 2010. This only made for SharePoint 2010.