Good points. I continue to experience the same frustration. My X1051 is just outside of a year old. For something sold at retail so recently, Sony should release a patch that allows the YouTube vids to play on the X. Or at minimum a reasonable explanation for why this embedded YouTube functionality simply won't work.
FWIW I'll continue to lobby Sony to release a firmware update. By phone, the engineer I talked to (3rd level support) indicated that a letter would be the best approach. So write them I will. And hopefully other X owners will do the same.
Let me know please if you make any further progress on the issue - thanks.