I opened mine a few days ago. Yes, it does stick more than the old 13, but when you pull harder it comes out easily. You just need to force it just a bit. Be careful that you remove every screw first, of course
I had this same issue today. I've removed the bottom of my girlfriend's 13" MBP, but today when first taking off the bottom, it wouldn't come off. Turns out, there are clips, as seen here: