As for getting rid of the navbar after rooting, I don't know. I haven't rooted mine yet, so I'm not sure what would be involved in that. Sorry I can't be more help there.

With the performance comparisons, the game I noticed the biggest difference in was Wrestling Revolution 3D. That game allows for twenty characters, a ton of weapons and props, as well as a bunch of modifications to the ring area all on screen at once with 3D graphics. On Ouya, having lots of characters and props can lead to some significant slowdown on occasion. The game runs consistently smoother on MOJO. A ten man tag match on Ouya might slow down several times while the same match on MOJO might slow a bit on startup, but catches up quick and plays fairly well from there. As for non-Ouya 3D titles, I run GTA: Vice City without problems. Hopefully that gives you a better idea of how the MOJO performs.

You are correct, MOJO does not have a power button. In fact, you cannot even tell it to go into sleep mode like you can with the Ouya. It just automatically goes into sleep mode after about ten minutes of inactivity. Just checked mine while in sleep mode, and the thing is room temperature. Doesn't seem to heat up at all, at least not externally (not going to take it apart to check inside). As for the sleep mode being connected to the Internet, it still receives push notifications while in sleep mode, so it apparently stays connected and still accesses data. As for the controller, it turns off when the system goes to sleep. One more thing of note, if you have it hooked up in a bedroom, you will want something to put in front of it at night, unless you could use a nightlight. There is a big blue light in the front of the console that is always on as long as it is plugged in. The room becomes bathed in blue at night.