Not sure if this also worked on U303, but as normal the stupid menu screen comes up when you turn on the Hopper. But today, I turned it on but instead, for some reason, of tuning to a channel, I left it up while I went to make my cup of coffee (K-Cup). When I got back the menu was timed out and it was on full screen to the last tuned channel. I can't testify that it did that on U303 but at least on U304 if you leave it alone the menu will go away.
My guess, 2-3 minutes as that's what it takes to turn on the Keurig, warm it up, make a cup and come back.
I'm not sure if anyone else let it timeout on U303, but if you still have it you can try to turn it on and see if it does timeout. If it doesn't then that might be one of the changes in U304.
I'll try it again tomorrow, and time the timeout value.