If you are rooted and on stock recovery accepting the ota will break root but will update providing you haven't removed the required bloat.
Accepting the ota with custom recovery will cause the ota to fail but will not brick the phone.
Many rooted people on ROM's they like, don't want the ota but are bothered by the constant ota notifications. They purposely accept the ota and let it try to install because once it tries and fails, you won't get any movie notifications.
Don't fall for the myth that accepting an ota while on custom recovery will brick your phone. Maybe on HTC phones but not on the GS3.