I have seen this question come up multiple times and I believe I have a simple solution.
I have found a way to maximize your results with a MCE remote receiver.
You need to program 2 devices into the Harmony, one is the
Windows Media Center SE, the second is
Microsoft MCE Keyboard.
When programming the HTPC activity be sure that both devices are included.
When you have both devices installed you get a lot more flexibility when controlling XBMC, Plex and your PC in general.
For Plex and XBMC the back key is "ESC". I programmed my remote's exit button to this, you will find that in the keyboard list. You can launch programs from the task bar with the keystroke combination of "Win+1" for the first item sitting on the task bar "WIN+2" for the second, etc...
I use Win 8 for my HTPC, the START key programmed to the Menu button on my remote jumps me to the Metro menu and the remote lets me select what ever program or app I want to run. I use the WIN+1 key to hot start XBMC from a button. I have come to the conclusion that Win 8 is the best choice for this type of application. The large metro menu screen works will on a TV screen.
Program the Up, Down Left and Right buttons to DirectionUp, DirectionDown etc.. The OK button is programmed as Enter.
The Netflix app plays better then the browser version, its mostly controllable by the remote but there are a couple of places that you HAVE to have a mouse
, as a plus the App plays 5.1 audio. I have tried the Plex app, but 5.1 audio is problematic, XBMC has won the battle at my place. I use Plex on my Roku.
You should not need to learn anything from a remote and you should find that you have a much more versatile system.
When playing video from an App:
Video adjustments can be set for Apps with an ATI video card, use catalyst to override the video settings when playing video, this also affects video playing from an App. I calibrated this by playing a test pattern DVD with VLC.
Hope that all of this helps.
Jim