I have to admit, I liked some of the previous 'depressing' music that was in Indev, I quite miss having it in Infdev. There was something soothing about patrolling my towers at night, with the dull glow of torches casting shadows on the walls, listening to soft and melancholy piano music.
If you bother to dig through your files, you can find the three different songs somewhere and put them on a playlist. (That way you can control the volume.)
I personally do NOT like it. It doesn't fit Minecraft well.
It would be better if he remixed the old songs to be a BIT less depressing. The ambiance works well, but it's too calm for certain moments, and it's too gloomy.
I would be giddy if it would stay ambient AND cheery at the same time.