This weekend I picked up a Logitech Harmony 550 universal remote.  I selected it to interface with my home entertainment center that has an Apple TV and a DIRECTV device.  Both have proven troublesome in integration.  However the Harmony quickly recognized the devices as an Insignia television.  Set up was a snap, under 30 minutes, except for the life of me I could not figure out how to properly configure the activities. The activities feature allows you to press a button that says "Watch TV" or "Watch DVD" and it automatically turns on the proper devices, turns off the unused devices, selects the right input for the television, and then sets the remotes buttons for proper use (i.e. the volume buttons still control the TV, but the play button controls the DVD player -- no having to go hit the device and select a new device each time you want to change functions).  Anyway, so the input would just not work properly for me.  Through much trial and error, here is how to set-up your Insignia TV on the Harmony:

1. Select the device, TV.
2. Review the settings for the activity and select the option to review the settings manually.
3. Answer the wizard questions until you get to the page that says "What input or channel does your Insignia TV need to be on?"
4. Even if it is on the correct input select, "Source input is missing"
5. Select Method 3.
6. Set up your inputs exactly as they are on the menu you get when you press the input button on your Insignia TV.
7. Select no to the question: "When cycling through inputs, does your TV skip over inputs that are not connected?"
8. For "Remote button displays source inputs menu" select InputNext.
9. For "Remote button cycles through source inputs" select InputNext.
10. For "Remote button confirms the source input" select Select.
11. Select no to the question: "When you select inputs from the on-screen input menu, is TV always the default selection?"
12. Complete the rest of the wizard.
13. Update your remote.
14. Turn off all of your devices and try it out.  It is possible that it might not work properly the first time.  If it doesn't use the help button and correct the inputs.  Once you do this for each activity it should begin working properly.
15. As a side note I decreased the input delay to 100ms to speed up the process for changing from one activity to another.

Good luck!