No issues here.
I regularly use both my Wahoo TICKR and my Garmin rigid strap HRM. Neither has had a problem before or during a ride.
Battery?
I recently bought the 520 and can't get it to work with the Tickr heart rate monitor. After a long wait, it did recognize that the HR monitor was there. It looks as if it's connected, but there's no HR data going to the device or showing up on the screen. It sounds as if Garmin has not fixed this issue since it first came up a couple of months ago. It would be nice to know if Garmin is planning to patch this bug so I don't have to go buy another device.