In the past I've been using a combination of Visual Studio 2005 and Visual Studio 2008 to develop Guineu. I finally upgrade Visual Studio on the build machine, as well, and moved development completely to Visual Studio 2008. As a user you aren't affected by this move since Guineu remains a .NET 2.0 application.
The past few releases mainly fixed a number of bugs: SELECT 0 does now move to the next free work area. Edit boxes have a vertical scroll bar just like in Visual FoxPro. Checkboxes deal properly with the Value property. Deleted records are not shown in the grid. Replacing a string field with an empty string clears the field now.