Ok here, her breast is to high up. And she is to thin, like if you look up her brest and think that they are moustlly made up of fat, and look back at her body you'll realize that this is really unatural, and could only be acomplished through plastic surgery! Ive cleaned up some higlights and I would recomend you to work more on the head!
here: http://img842.imageshack.us/img842/9394/pinup2.gif
@ inqOrius - Generally no, I didn't use a reference...I'm trying to train myself to draw these from scratch. I did use various images for rough proportions here and there, but nothing for the pose itself.
Chest messed up? How so? Could you do a quick edit? I know it's not perfect, but I can't see it. How bad is it?
Glad you like the legs and butt. 
Her chest is messed up!
But good work on the legs and butt!
I like the idea and pose, but the proportions seem odd to me - did you use a reference?
Nice edit. Thanks.
What about a support bra? lol Yeah I see what you mean.
But the head? I'm at a really small scale here. Wrong shape? Too small? Too far left? Right?