Well, I bought the ViewSonic N3760w and a Harmony 550 remote, and after a couple of days of trial and error I was able to make input switching work 90% correctly. (Which is great, because I really need the Harmony, since ViewSonic provided no remote codes for use with other manfacturers, meaning my Sony DVD/VHS remote cannot control the TV.)
I have a VHS deck on the AV1 input, HD cable on the HD1 input, and a DVD player on the HD2 input. (It's actually a combo VHS/DVD deck with separate outputs.)
I think the problem that most people have switching inputs with a Harmony and the ViewSonic is that the ViewSonic has a little bit of all kinds of input-switching methods. You can switch via menus and arrows, or by scrolling up and down in a list, or by input buttons. Input buttons are the most precise method, but ViewSonic cheated: The TV button on the remote goes to the ViewSonic's tuner only, but the AV, HD and HMI buttons each go to *two* inputs, toggling between the two:
AV button = AV1 and AV2 in succession
HD button = HD1 and HD2 in succession
HDMI button = PC and HDMI in succsession
If for instance, you press the HD button twice to get to HD2, then press the AV button, then press the HD button again, you will be back on HD1. But if you have the TV set to HD2 and turn it off, when you turn it on again, it will still be on HD2, but an HD button press will get you back to HD1.
You can see why the Harmony gets a little confused.
So, after trying a lot of different things, I told the Harmony that I had discrete buttons for each input, even though that's only half true. So now, if I turn the TV on and select "watch TV/PVR," I get the right input (HD1, where I connected the cable). If I then choose "watch DVD", I again get the correct input, because the HD button command switches to HD2. If I then switch to "watch tape," the Harmony correctly switches to AV1.
This is where it gets tricky though. If I then go from "watch tape" back to "watch DVD" the ViewSonic switches to the HD1 cable input instead of the HD2 DVD input, because it always goes back to the first of the two.
My solution to this problem was to create a custom button in both the "watch TV/PVR" and "watch DVD" activities, labeled, "Swap TV/DVD." This button simply sends the HD command again so that whichever HD input was on, I get the other. If the input was wrong after entering the activity, this fixes it in one step.
It's the most elegant way I can figure to handle the problem for my configuration. Your mileage may vary.
I also do not allow the Harmony to power on or off any of my equipment. This is because the Motorola HD/PVR box malfunctions if you ever turn it off, and doesn't get the updates Comcast sends in the middle of the night; and because I'd rather turn the rest of the equipment on and off without the remote than have to deal with power-switching Harmony issues.
I hope this is helpful to someone else. Happy tweaking!