I've seen a few Windows 7 applications popping up around the web that take advantage of the new task bar functionality. However, some of these applications are treating the task bar like the notification area. There is no foreground window. All interaction is done through the task bar button (with overlays, progress bars, jump lists, etc).
Personally, I like the new task bar more than the notification area because I have the ability to use larger icons and give the user a very familiar user interface with a rich experience. But I also feel like applications like those described above should be kept in the notification area.
What do you think about applications that use the Windows 7 task bar as the "new notification area"? Should it be avoided?
Microsoft is doing its best to discourage use of the 'notification area', frequently referred to as the 'System Tray'. Instead they encourage more detailed and interactive application icons. For example, the progress bar that's visible on the explorer icon when you're performing file operations in the explorer.
Read the windows user experience interaction guidelines for more details on the new recommended functionality.