Ha! That was kinda freaky, cuz I couldn't remember starting this post. My name's Ada, btw. =P
I just saw Overgrown in person today and, though they didn't have Bitter to compare, the MA said Overgrown's a Satin which should be much easier to apply. Overgrown is also not as bright (I'm guessing she's referring to the yellow in Bitter) so perhaps more useable for most. Perhaps someone who's seen both in person can confirm/comment?
HTH!
On a side note, they said something about Bitter not being available to dept. store counters, only at the MAC stores. Has anyone else heard about this?