Actually, I went for my first one today. I'm a couple of years past when I should have started, but I put it off, and put it off...
And then on our first day at WDW earlier this month, I noticed a lump while I was showering (my disorganization paid off - I had forgotten to pack my "puffy", and the lump was easily felt with soapy hands).
Anyway, I had a mammogram, followed by an ultrasound that indicates a benign fibroadenoma. I'm going in for a follow-up and most likely a biopsy next week, just to make sure.
I do monthly self-exams, and I just had an exam in the doctor's office in early June, but the lump wasn't felt by me or the doctor. Luckily for me, the tumor appears to be benign but I can tell you that I've spent the last 3 weeks kicking myself for not getting that baseline mammogram when I turned 40. Worrying that I might have cancer while at the same time dealing with the reality that my FIL is dying from pancreatic cancer was no fun. I was panicked about how my poor husband would be able to deal with me being sick while his dad is dying, how I could convince the kids that just because their grandpa is dying of cancer doesn't mean everyone that has cancer will die, etc.
Anyway, probably TMI, but I would HIGHLY recommend the baseline mammogram at 40, and I would also HIGHLY recommend doing the soapy-hands-in-the-shower in addition to the flat-on-the-back-arm-behind-the-head self-exam.