I would expect one advantage would be an SA number for incoming calls, I wonder how many concurrent calls the system could handle (i.e. at least one in, one out simultaneously). I would also expect an Iburst modem/device and free bandwidth from them for their price - that should allow some QoS.
Most of the VOIP guys are charging R0.25 per minute for international, so R699 equates to over 2500 minutes per month on one line or just over two hours per week day, every day. Pretty intense if it is one line only with no QoS data connection.
Nice to see some fixed price options filtering in to the market though, good work for trying Iburst, think you missed a bit, but at least it is an attempt. I would like to see more uncapped type call options hitting the market, Telkom how about unlimited local calls...