I never had problems understanding laid back in ECSTASY. It's pretty clear for me, I always wondered how you can hear something different, lol.
Though I have the same problems with Under, Lay Down and Lollipop.
For me Kuu is often really good with her English and sometimes pretty bad, a hit or miss.
Namie's Engrish is the worst for me as well.
WILD is just horrendous...
From her new songs Only You is partly really bad as well.
But it's pretty good in In the Spotlight (Tokyo)!
She gets better and that's great!
