I've seen some pretty scary numbers on the effect of 3-D Secure payments to conversion rates. I guess it's really hard to do The Right Thing™ on this matter.
Numbers for good or worst? They help A LOT fighting fraud. I think a good solution could be implementing it on Stripe.js.
The latter. It's probably a combination of breaking the UX by redirecting the user to his/her banks' website and the crappy forms the banks made for this.