I hate to answer my own questions (especially that fast) but I made it work with VS2008:
- Get reportviewer.exe from location indicated at the link above or from the cab6.cab in the VS2010Beta2 disk.
- Install it.
- Copy Microsoft.ReportViewer.WebForms.dll and Microsoft.ReportViewer.Common.dll to your app's local dlls folder (\lib) and reference them in the project. Not sure if this is enough, I had to deploy/install reportviewer.exe anyway. But this is required to add references to VS2008.
- Now the report viewer - at least, LocalReport used to generate PDFs - work.
I couldn't reference the assemblies in the GAC with VS2008 "Add Reference" - it only showed 9.0 versions. Don't know why, though of course it would be better to reference GAC assemblies. Will accept those who provide a fix for this.