Update: I got the Roku. It works, but it's clunky to use and took an hour to set up, due to the Roku iPad app's keyboard refusing to actually send a password to the unit. Also, the interface wastes space on pushing paid content that could be used to better purpose.
But the worst thing is the total lack of audio-out jacks, so it can't be cabled to my hifi's preamp or standalone DAC. (I'm using optical cable from my ATV3 to the DAC.) The only output is HDMI, presumably because only an idiot would not be using a home theater receiver. Guess what? I'm apparently an idiot, as I don't have or need one. I could run RCA cables from the TV to the preamp, but that means using the TV's DAC and lots of additional TV circuitry, which doesn't sound as good. I also use the ATV3 to stream uncompressed music from iTunes on my Mac, and so would need the TV on to listen to music.
So...I looked the current Apple TV. It, too, has only HDMI output. Apple decides what we can do, and we can like it or lump it. Feh. Tbe $149 ATVHD has no apparent advantage over the $24 Roku. And its remote is awful.
So, I suppose I'll use the Roku for YouTube, without the ability to run the audio through real speakers, and continue to use the ATV3 for everything else. Our world of choices is going steadily downhill...