Replicating MySQL over the WAN

I am researching how practical it is to do real-time replication of a MySQL database over a WAN SSH tunnel. What are the constraints caused by bandwidth, MySQL *blocking* bugs (apparently there are a few out there in older versions of MySQL such as 4.x) and how real-time is the real-time replication. How well does a Master/Slave or a Master/Master MySQL system work in this case?