I got a launch day Xbox One, which I'll post about soon. It's awesome. At any rate, when I was setting up TV integration, I had some issues getting my Mitsubishi DLP set up correctly. I figured I'd post about it in case anyone else had a similar issue.
My TV is a Mitsubishi WD-73840 DLP, and it's a great display for film and video games. It has nice, accurate colors, great motion, and it's kinda huge. That being said, it's also kind of an uncommon display when compared with LCD and Plasma televisions.
The wizard that the Xbox One uses to configure your TV has a couple of menus. The first one is a list of manufacturers. Mitsubishi isn't there. You need to select "I don't see my brand", then enter part of the name. If your TV is the same model as mine, your remote code is gonna be T3500. Manually enter that and you're off to the races. If yours is a different one, you'll have to jump through some hoops. That's where it got tricky for me. The first thing the Xbox will do is fire some IR commands out, the first being "Mute". Make sure that it only mutes and unmutes once. If it's muting and unmuting several times when it sends the test code, it's the wrong one. If you allow it to decide to use that code, it won't be able to turn the TV on.
Anyway, after getting it set with the correct code (again, that's T3500 for the WD73840) saying "Xbox On" turns on my TV, satellite receiver (HR34 from DirecTV) and audio receiver (Denon AVR1612) as well as the Xbox itself. It's pretty awesome.
Hope this helps.