The biggest difference, imo, was released in 6.1 and is the event structure. Instead of polling the front panel controls, you use the event structure. There's also .NET support, Express VIs, custom probes, a tree control, and many more. For all of the changes, you should refer to the LabVIEW 7.0 Upgrade Notes. It's part of the LabVIEW Bookshelf. The NI Example Finder is also changed and there's a section on the Browse tab for "New Examples in LabVIEW 7.0".
