I read somewhere that only 25% of women do.

No most don't. It's not as common as people on here make it to be.

Definitely not. It also varies from pregnancy to pregnancy. I had implantation bleeding the very first time I got pregnant, but not at all the next two times.

nop, but I had ovulation cramps as well as implantation cramps.

I only had it with my two previous pregnancies not this one. It was basically some brown discharge and when I would wipe a little pink on the day my period was due. Then it all stopped.