I used it. I was on it for about 8 months when I tried it. So I gave it a fair shot. It didn't help me much, but it's been known to help so many women to regulate their cycles, reduce pms symptoms, among other things (it's been awhile so I don't recall all it's benefits). I would get periods on my own while on Vitex but I was charting my bbt and it didn't seem I was ovulating on it.
I haven't used it but my sister did for non-TTC purposes - she has endometriosis, irregular cycles and really painful, heavy periods. The vitex, also called chasteberry, helped regulate her cycles and lightened her flow a little. Because it's an herb with very real medicinal qualities, I would suggest you do a lot of research or talk with an herbalist about it before using it, and keep in mind that it could likely take a while (possibly several cycles) before you start to notice a big difference.
I used it while TTC at one point and felt like it messed with my cycle more than helped it (I have shortish LPs, 8-10 days). Having endo to some degree that causes severe pain around AF, I did notice it tremendously help with that. But for TTC, I wasn't a fan.