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Is it just me or is Karaoke for the OP/ED of an anime the most useless thing ever?
It's just you.

Actually, I really appreciate it. Even in my native language (English) I sometimes have difficulty hearing every word of dialogue or lyrics, especially when there's background noises/sound effects &/or people are not speaking clearly (or are speaking 'in-character' in some dialect of Mumble).
In the case of ramanji (

), I like to be able to follow the syllables along and try to get a better sense of where word breaks are, as well as being able to visually verify what the sounds are that I'm supposed to be hearing. Will it teach me Japanese? Certainly not. Does it help me develop a better sense of the heard language? Definitely. No matter what language I'm listening to, even if my vocabulary is stunted, I'm always trying to pick out recognizable word- and grammar-forms ... which is the first step toward vocabulary building.
I'm very happy when I have the karaoke, not only for OP & ED, but also when there are songs during the feature. Do I wish I had more control over displaying it ..? Yep. I also am happy when I see subs & karaoke available with creative options. It sure would be nice to be able to enable/disable multiple subs, such as: main dialogue subs on/off, karaoke on/off, and/or signs & background chatter subs on/off ... any combination of those three at any time would be a nice option to have control over.
In addition to being able to modify the font & color & placement for each.
Hell, I'd love to be able to turn kanji on and off in combination with romanji; I could be using a good portion of my anime-watching time to also build my reading vocabulary. It would be yet more amazing if there was another sub-stream where the very literal English translation of word forms followed along with kanji & romanji streams. No, I wouldn't want them all on simultaneously all the time, but having the options would be an awesome language tool.
I'm sure it'll be possible some day, and having extra karaoke & signs 'always on' with my subs doesn't annoy me enough to get all that upset with it.