Life is too short to read through this massive thread, so this is probably mentioned many times already:

Scrolling through search results slows down to a crawl as time goes on.

Pressing same button (e.g. search, play) many times opens the same window many times. The button should be pressable just once, really.

After you use the app for a while, it slows down enough to be unusable and needs to be restarted.

Apart from bugs, app looks good and does what I need from youtube app, so keep up the good work.