OPK's vs CBEFM anyone tried both?

I used both actually. I have been through three CBEFM's, every time we start ttcing, I just buy another one off of ebay and than I resell mine on there instead of holding onto it. I loved them, it took the guesswork out of it for me and was always right on with my O day. I temped and used wondfo opks also just for reassurance, probably overkill but they were always right on and I always got a positive opk on a peak day and had the temp shift with my temps to verify i had actually ovulated. I bought the sticks off of ebay also brand new. I would definately check ebay, you can reset the monitors to your cycles and alot of people throw in extras also, I always throw in any opks and pregnancy tests i have left along with sticks for the machine.